Good Puerto Rican/Cuban grocery?
Any specific neighborhood?
I'm from PR & live in Kips Bay & find yuca & plantains often in Gristede's & Food Emporium.
Hubby says he can get anything we need where he works (Lower East Side) as well as anywhere around Alphabet City. Obviously around the 116th street 4/5/6 trains (one stop north & south as well). Walk out the station and you'll be surrounded by anything & everything you need!
What are you making?
Some of the ingredients that you mentioned are found in many latin cultures. Of the above some of the best Longaniza that I have tasted in NY comes from a Mexican butcher / bodega in Bushwick / Ridgewood section of Brooklyn. Spicy meaty sausage that absolutely full of flavor and aroma. They do not speak much English in this store but the sausage needs no explanation. This store is at the corner of Seneca Av and Menahan St, called Bravos Meat Mkt. Bit of trek from Manhattan but definitely worth if for the Longaniza.
There aren't many "Puerto Rican" neighborhoods in NYC anymore (they're mostly Dominican now) but your easiest bet would be to go up to Washington Heights. (There used to be a row of grocery stores and bodegas across the big intersection from the 168th St. subway station.) You could also go out to Jackson Heights - most of even the big supermarkets carry a wide range of Carribean/Latin Latin American stuff.
Yucca and plantains should be pretty easy to find even in non-Hispanic neighborhoods.