I don't live in the USA, so I can't comment on what they actually do in practice. Even if the whole thing about the Democrats is true, what if they happen to be the most well-organised and doing the best work in your area? That could be a consideration.
Other than that, normally joining a communist party is a serious commitment. I don't know if this holds for the CPUSA as well, but if not, it should. A real communist party doesn't do revolving-door internet recruitment, but it expects its members to get active, and offers them hands-on education. So under those circumstances, I would never join an organisation unless I had a clear view of what this would mean.
But it should always be possible to simply give the party a phonecall, visit them or have them visit you, have them send you some literature, attend events, get involved with a front organisation like the
youth league if you're younger, etc., and generally be an active or semi-active sympathiser until your mind is made up. That's always better than just jumping in.
I don't think they consider Obama a socialist, in any case. Their position on the Democrats, which seems misguided and opportunistic to me, is presented as purely tactical.
At the moment, the CPUSA happen to be in their pre-Congress discussion period, so there are loads and loads of discussion articles about what the future line should be. It remains to be seen what will actually happen at the Congress (in June). You should read some of the
articles and see if they can help you make up your mind. Also a few other, more critical articles at the top of
this page.