There are events in San Francisco almost everyday where you can meet startup folks. Not to downplay YC but the YC community is just a small part of the startup community in the Bay Area.

With regards to meeting seasoned entrepreneurs, just go to events and you'll meet them. Most of them are very generous of their time because they just want to help fellow entrepreneurs.

Just remember though especially with meeting investors that you are one of thousands in the Bay Area that wants a face-time with them.

I haven't really talked to investors. I ask myself why I am worth their time. In my opinion, I haven't done enough to warrant an audience with them. Well, not yet. ;-)