When I go to clubs I tend to drift away from my friends, and so I end up looking like I'm alone when I talk to people.
Most guys who go to clubs, however, have that "I'm going to a club alone and I'm scared" vibe when they arrive. If you're 100% there to have a great time, then by all means, go for it. Anything less is tough though.
On the other hand, I'd ask, why go to a club if you're not there to 100% have fun? Guys to go to clubs just to pickup a girl reek of desperation.