I think you'll be OK, though as others said, it does depend upon state law. I live in MD which is not shall issue (actually getting a permit is nearly impossible unless you are a business owner with large cash deposits or you are politically connected), so I can't carry here. Other than VA and PA (the states where I carry most often and thus am most familiar with the laws), I usually just assume that the gun must be completely concealed as some states can be pretty harsh if you print or your covering garment reveals the gun. In those cases, I go with the smallest gun and most concealable carry method. As others have said, most people won't notice, but then, most people are polite enough (or scared enough) that they probably won't let you know if they notice the gun anyway so I'm not taking any chances.
Unless I see a man who's openly gay (not being pejorative), I assume any guy wearing a fanny pack is carrying.
Hmm, gay men tend to be more fashion conscious than average. Yes, it is a stereotype, but from what I saw when in my retail days, it is often true. Granted, I have had gay friends who are far from that stereotype, and straight friends who are quite dapper (I used to be as well), but generally, I think it is the middle aged family man who is the most likely to be wearing a fanny pack if he isn't carrying.