Absolutely, it was fine for you to join! They wouldn't have allowed you to if it weren't!
FTR, when a CSR asks you how you heard about them, they're asking for marketing reasons -- just making sure WHERE their marketing dollars are best spent.
F'r example, if you tell them that you heard about their great customer service (or product) via a friend, they'll more than likely begin offering current clients/members discounts, rebates, incentives, etc, to refer MORE friends.
If you tell them you heard about them at a particular forum, if that site is dropped often enough by new clients, they'll more than likely step up the advertising with that site.
If you tell them you saw their ad in the yellow pages, you can be sure that next publish, they'll have a BIGGER ad.
It's all marketing!
Anywho, we've belonged to USAA for the past 13 years -- you'll LOVE it. They're the BEST!! And yep, if the result is that they'll offer even better discounts (though I don't know HOW they could), you can tell'em I said that!!