I'm not out to most of my friends as a less wrong reader and aspiring rationalist because I'm worried that they'll think that I've joined a phyg! I don't ask guys out, and I'm even too scared to go to the local less wrong meetup because I'll be older than people and I worry they won't think I'm smart enough.

I hate the "phyg" coinage so much. That said, I've had a decent amount of luck introducing the LW meme cluster to people as a toolset rather than an identity, thus avoiding all the heuristics that get triggered by "hey, mom, wanna hear about this new philosophy of life that I've started identifying with?" Ideally, the name of the site should come up much later: start with the stuff your audience would find useful or interesting, and if that works well, you know where to find more.

Truthfully, I'd say that's a better way to approach it even if you aren't trying to build community.

As to LW meetup demographics, I wouldn't worry too much about age. If you're older than most of your local group, that's if anything a status positive, and expected intelligence isn't likely to be much of a problem either; bear in mind that what you see on the site is filtered for some level of domain knowledge, thanks to our norms against spinning bullshit or repeating popular beliefs without research. People, especially young people, tend to come off as less knowledgeable and eloquent in person.