I get bored nowadays grabbing. I'll go 8-12k AGl and beeline to the fight. Sometimes I get higher as I've alt-tabbed to read the bbs.
Really though, the question isn't at what altitude do you prefer to enter a fight. but what altitude do you prefer to dogfight at.
I prefer deck fights.. that way my chosen opponents can't decide they are getting waxed and dive out....hate chasing my victims. for long periods of time.