I am about to visit Boston and I would really like to find a store that sells Portuguese food, especially sweet bread, salted cod, chorizo, and fava beans!!!! I live in Texas, so I have no way to get those things unless I have them shipped, which is super expensive. It would also be helpful if I could reach the store by subway or trolley since I won't have a car. Thanks!
What day of the week will you be in Boston and where are you staying? Most Portuguese stores in the area close fairly early during the week (6pm), then are open all day Saturday, and some are open Sunday mornings until either Noon or 2pm.
As mentioned with the recommendation of Roma, you could do one-stop shopping for these items in most Portuguese stores. I think the store mentioned for Union Sq (Maria's market) no longer exists -- there have been several incarnations of Brazilian markets in the same location. Union Sq is an ok destination -- with some foot work you could have lunch at J+J's, shop at Roma, and perhaps shop Jerry's liquors (which has a good selection of portuguese liquors). However, it would be a lot of zig-zagging and I think you would be better off on Cambridge St, in Cambridge (East Cambridge) where you could see more with about the same output of energy and less mapping out destinations beforehand.
To get to East Cambridge from downtown Boston, take the Green Line to Lechmere Station. The 69 Bus runs the length of Cambridge St, but if the weather is nice you may just want to walk (if its windy, Cambridge St can be really cold because of its orientation and proximity to the water). The 69 is also the best access from Harvard Sq (and or Allston via Harvard).
I do most of my shopping for Portuguese goods at Courthouse Seafood that 9lives mentioned. Its run by two Portuguese brothers, who along with their sister run a seafood restaurant. Ask the 69 driver to get off at 6th St and walk back towards Lechmere 1/2 block. The have whole salt cod pieces (both skinless/boneless and with bones in boxes) for usual prices, plus a discount (2lbs for $10) for remnant pieces in plastic bags with the skinless/boneless. Make sure you look in the plastic cans for portuguese olives and marinated peppers, and they have various seasonings both packaged and colorau, nicer olive oils, etc. I prefer the smaller favas (in the freezer), but they don't always have them. They have local chorico which I find to have a very earthy flavor, as well as queijo sao jorge (which suffers here from being refrigerated a bit).
Continuing up Cambridge St, 660 Liquors just past Fulkerson St has one of the better selections of Portuguese wine and a number of liquors (Jerry's has a more selection of ginginha). You can get fried fava beans at the counter to snack on as you hoof down Cambridge St.
When you pass Cardinal Medeiros Ave and St Anthony's Church, there is a small store front for Central Bakery. They offer fresh sweet breads and muffins, plus broa, just don't expect the easter sweet bread (folar da pascoa) with eggs this time of year. They never used to carry sweets, but have been carrying some excellent ones from Chocolate c/Pimenta in Fall River (Casal has slipped a bit, so I tend to buy these).
Pires Market just past Sunset Cafe is a Cape verdean market with some portuguese goods, but a bit disappointing these days. Close to Prospect St and after the railroad tracks, Cambridge Market LLC used to be the largest Portuguese market on the street, but was sold and is now more of a convenience store with some Portuguese/Brazilian products (they and Casal carry some portuguese CDs). If you stay on he same side of the street, just after Massachusetts Alliance of Portuguese speakers, is a small, non-descript store that is often closed, but sells some portuguese cookware and stuff.
Casal Bakery is roughly across the street and although most of their business these days seems to be Brazilian oriented goods, they have a large selection of Portuguese sweets -- both baked there and imported (nice not too-sweet wafers). Their quality had slipped, then improved a little over a year ago, but the last few times I have been a bit disappointed and have been buying sweets from Fall River at either Central or Courthouse when freshly delivered.
Fernandes Fish market is just a few doors up the street and is a small store with a huge selection of portuguese products (significantly more than courthouse, but less fish). This is a good bet for cheeses, coffee, etc. I have had a few issues with freshness here, but it is a must stop.
Martin Brothers Liquors across the street is cash only and has the cheapest prices on some Portuguese wines, but 660 has a much larger selection. Superior Market a bit further toward Inman Sq is a Portuguese oriented convenience store, but nothing too special.
You might want to try both the linguica/chorico from Courthouse and Fernandes, as well as a slightly more commercial brand such as Gaspers (who also make a nice, more lightly spiced, morcela).
Courthouse used to close at 6 on weeknights, but I believe they now stay later (until 7pm?). Courthouse and Central Bakery are definitely closed on Sundays. Casal is open Sunday AM and Fernandes _might_ have some Sunday hours. Previously both liquor stores were shut on Sunday, but I think at least Martin Bros is now open and possibly 660.
New Deal Fish Market (at the corner of fulkerson after Courthouse) is Portuguese owned, but has less portuguese products than the other two. That said, when they do carry portuguese cheese they store it at room temperature and its excellent.
Whenever you get hungry, there will be a Portuguese restaurant nearby :-)
Roma Seafood is in Union Square in Somerville, across the street from Target. They have all the things you're looking for. The 87 bus from Lechmere stops right in front, or the 86 or 91 buses will drop you off in Union Square, just a short walk.
Make sure you get the spicy linguicia at Roma. It is amazing!