In our lessons, everyone dances because we are all on the floor working on a concept, moving from partner to partner at the end of every song. But a dance, a milonga, is different. And, yes, those can be more of a challenge for people who are new to the tango. At our dances, the experienced dancers tend to dance with other experienced dancers -- not because they're stuffy but because that's who they know (and often have been friends for years via tango). Even those who are new to the tango tend to only dance with those who are new to the tango too -- the people from their classes. If you start coming to the social dances regularly, people will notice. "Hey, I saw him/her here last time, and the time before that too. He/She must be serious about tango." And then they approach you ... it does take a while. That is why starting at the beginning level and working through the series of classes is a really good idea. You not only learn how to dance the tango, but you also start making friends and those are the people you'll start dancing with at the social dances. Once others see you dancing, then they will ask you to dance too.
On a personal side note, I think that the Sacramento Tango community happens to be the kindest, funnest, coolest group of people I know. They love to live, they love to dance, they love to laugh and play and ... really, how cool is that? They are also, I think, very approachable and easy to get to know. Just come up and say hello. Introduce yourself. At the milongas, come to the table in the back, pull up a chair, introduce yourself ... and the rest, as they say, is history ... tango history.