Looks like everyone has given you some great advice on the subject you raised. I think a lot of people have gotten their fair share of disappointment when trying to group with others to play music. I'm guessing it can sometimes be hard to find like-minded people. Either that, or egos get in the way. I've found that too many people are over-confident that they're going to become rockstars, and they miss the point of the collaboration.
When I began playing again and felt ready to start jamming with others, I visited two places on the net where I could potentially find other players: 1 was a musical forum for my city, and the other was craigslist.com. Both sites had sections for musicians seeking like-minded players for various projects. I was looking for something less serious, and more focused on having fun and being creative. I eventually found 2 great guitarists, started jamming, and have been having fun ever since.
After we had gotten good enough (in our heads lol) to try some open mics together at cafes and bars, the opportunities to find other jammers multiplied again. These open mics can be a haven for musicians of all ages who are seeking to show their music and express themselves. After getting to know some of them, I now find myself trying hard to find time to keep up with all the jams. Also, we often meet at parks during the summer, and when people hear our jam, they also join if they have their instruments. I remember several afternoons that were spent jamming with a group of 30 other people of all ages, playing all kinds of different instruments.
Of course, there will be those that you encounter who are either arrogant, selfish, or deluded with ambitions that even they cannot live up to. I've had my share of them, and also those that weren't like that, but that I didn't share a musical connection with. Sometimes, it is easier to play by yourself, but I would recommend not giving up on trying to share making music with others. It's both fun and an enormously insightful learning experience.
In any case, I hope you find what you're looking for. The websites (check your local craigslist and musicians' forums) and open mics really worked for me.
Good luck and good jamming.