Rumbas are mainly in NYC. Here are a few options.
1) Central park rumba Sundays from 5 to 10 pm on warm non-rainy days (usually over 70). It has its pluses and minuses. On the plus side, it is good practice because there are usually some really good drummers that show up and sometimes a good rumba singer or two. Great place to learn to sing coro if the good singers are there and the coro doesn't cross the clave. Great place to practice guagua once you have it well-rehearsed and solid. On the minus side is the overemphasis on guaguanco, it is too loud, plus the guaperia, egos and overly fast tempos. Also, playing a yambu will usually get you kicked of the drum because few singers know how to sing it and few players want to (or know how to) play that slow. If it does fly, it usually turns into a guaguanco within 3 minutes. Great rumba columbias do happen, but are rare and depend on who is there. I plan to go today around 5 or 6.
2) I am told there are still some good rumbas at Orchard Beach in the summer, I haven't been there in a few years. Watch out for clave cruzada. My friend did a tambor (bata) there last week and said there were a lot of people.
3) Once you get to the level where you can hold solid time on tres dos or tumbador, the Zinc Bar rumbas are open and are modern Habana-style rumba. Not sure when the next one will be, schedule is very irregular now as some of the core group members are touring with other groups. The September calendar as of today has only 4 of the 30 dates filled in and the rumba is not on it yet. Check
http://www.zincbar.com next week to confirm day and time.
4) If you want to take great classes in playing rumba, Joaquin Pozo is teaching at the NYC Musicians' Union Local 802 on 48th St in NYC. He has a deep history in rumba and is one of the best conga players in the US, especially playing 4 congas with a band. He does charge but the price is great for a 1.5-2 hour class. Next class is Tue Sep 4 from 6 to 8 pm, but usually classes are on Wednesdays with some flexibility depending on students and Joaquin's gig commitments. Students are mixed levels from beginner to advanced, usually 2-4 per class. I can give you details, contact me at {gfj7 at optonline dot net}.