Good advice from Diane & Champion above.
As for jamming with a local band I recomend that you look up Dennis Wolfe & the Usual Suspects band. They play several days a week around San Pedro and they love having some outside talent sitting in. You may want to contact them when you get there so they can bring extra Guitars for you
Dennis & the band have a bunch of the Jerry Jeff Walker fans play with them during his several visits to San Pedro
Also All Cayed Up Band plays at Crazy Canucks Bar & Wet Willy's bar (Blues, and a little bit of everything)
There may be some other bands jaming, but I am not sure who is in town in August.
Have a blast. I always do!!