I have not gone to bars alone but I hardly go in big groups...2 or 3 of us is usually it.
As far as talking to people, I will almost never start a conversation with a guy (I have a buddy that does that all the time and it turns super boring, to help ColoHusk out, his initials are GW) but I will chat up girls all the time (I am sure that 90% of those chat-ups result in the girl committing suicide or at the very least, thinking about it)
I also have Bar-ADD...If I get bored or if there are no hot girls...I usually always want to leave.
I don't talk to too many guys at the bar, but sometimes its good, especially when alone, to gain some type of social proof within the bar. You'd be surprised how talking to a guy for two minutes and buying him a beer will do wonders, him now wanting to introduce you to all of his female barmates! I am also always very polite and cordial to door staff and make a habit of tipping bartenders well and getting to know them so that they become allies when in the bar (many also have some damn interesting stories/life experiences). However, it is pretty easy to tell when other guys are focused solely on the poon and aren't interesting in talking. No point in holding them back or cramping their game.
...and I fixed the second part to apply to my stance on "Bar-ADD" (you should patent that).