As for group rides, I guess you'll have to PM me, cause there really is no group on the island that meets regularly. As was said before, the best rides are in Clear Lake.
So as for things to do, the strand is nice, perhaps a little tourist, but if the weather is nice, its a great place to hang out. So go to the strand and catch some lunch. There are plenty of restaurants in the strand, I recommend the "Mediterranean Chef" on 24th and Strand for a healthy authentic restaurant.
After the strand, take a quick hop across the island, 2 minute drive max, and head to the seawall. Once there go to "The spot" and sit on the deck and catch a beer. thats at 35thish and seawall. If you really want to be a local, go to "the poop deck" a dive, but sit on the raised deck outside, its great.
Before you get some beers- take an easy bike ride down the seawall if you wish its a nice ride.
Gaidos is a good seafood place on 39th street and seawall, its locally owned and operated, nice place. I have a million good ideas if you want more PM me.