bar near frances?
Starbelly might be a nice prelude to Frances, but that's if you can find a seat at the bar. The restaurant as a whole gets pretty crowded. There's also a new lounge-like restaurant but I can't think of the name right now. It's right next to the Chevron gas station at Market and Castro.
Frances is on 17th between Noe and Sanchez.
This is one block from the ground zero of the castro, and there are tons of bars in the area, most of them gay., but all of them will be straight-friendly (don't know what category you fit in here...) You could entertain yourself for hours barhopping there, walking along Castro between 17 & 18, and/or 18th between noe and diamond.
"The Mix" on 18th between Noe and Sanchez is very mixed. Regardless of sexuality, sex, or age, you should feel comfortable there, and there is an outdoor smoking area in the back. It's quieter than some of the other bars in the area. It's the one bar I'd recommend to anybody without knowing anything about them.
The Mix is not a place where they "craft" their cocktails, that is harder to come by.
I'd advice Eureka Restaurant and Lounge, which is conveniently right across the street from the Mix. So you can compare. :-)
Blush! is a newish wine bar in the neighborhood, on Castro in between 17th and 18th. Quiet spot, good for conversation, a lot of seats.
For a divier place, Lucky 13 on Market is always fun, many beers on tap and by the bottle.
Starbelly is going to be a tough place to grab a drink, most of the people at the bar are eating. If you give it a shot, they have a very nice Cabernet-Sangiovese blend from Baja California, of all places.