I say take what your comfortable taking. My philosophy on my first trip was that I wasnt sure if I would ever do it again, so I wanted to make sure I did it right. I ended up taking 4 tabs and then 2 and a half more in the first 3 hours at a Classic rock cover band festival on April fools day. But I dont claim to be a good role model! That being said, two tabs will hopefully wreck your shit, and if your like me...thats what your going for. Stay home and wreck your shit though. On my first trip, at first I was really having a great time, I was openly smoking pot, and I thought everyone was on drugs! Then I realized I was surrounded by families with kids and shit and I was sure they all knew I was frying my balls off! I very quickly felt very uncomfortable and had to get away...luckily it was held outdoor at a park and I was able to find plenty of space when I needed it. later I realized everyone was on drugs and the sound tech was hitting a bong the whole time, but my perception was askew at the time so I freaked myself out for no reason.
Also I think the OP may be thinking that LSD is a more social drug than it actually will prove to be. You most likely will not want to go to parties with strangers, and rap is about as good for a trip as say...a punk rock show. drunk angry people everywhere has its time and place, but its not in the middle of a trip! I say just hang with the lady friend, split the acid if shes down...sex on acid is great!