I found this Web site very useful. There's a lot of info on local Salsa events and classes.
Beverley Ann Rees teaches Salsa at Sport and Health club in Tysons Corner, VA. She's good at teaching dance techniques for beginners, imho. Pace is very slo-ow. As slow as the slowest student. Students were mostly over 35. Pay was 40$ per month (4 classes), if you miss a class it's gone. Additional classes in the same month have discounts.
Cecilia Villalobos teaches Salsa in Virginia Ballroom. She was charging 55 for 5 classes, but you could use these classes any time. It's very convinient. The classes are very different from Beverly's. Students are mostly young, under 30. In the beginning everyone excersizes foot-work for 20 minutes or so, then she shows one combination. After that students practice this combination for the rest of the class switching partners. She has a couple of really advanced guys helping her, so you can ask for help anyone of them. At the end you bring your ticket and she punches it. You can join a class any time and buy a ticket.
Unfortunately VA Ballroom web site is down, so you can check this out.