Get an aluminum frame.

1) You're new to the sport, so why drop $2000+ when a bike that costs $1000 - $1500 will ride just as fast, and almost as smooth?
2) If you wind up truly love cycling, you're likely to want a second bike in a few years. The aluminum will be your beater/backup bike.
3) The weight difference is negligible. For example, the Jamis Xenith Comp (entry-level carbon) is $2000 and 19.75 lbs; the Jamis Ventura Race (good-quality aluminum) is $1400 and 19.75 lbs. The performance differences are unlikely to be worth the extra $600.
4) Last but not least: Don't buy a bike you can't afford to replace. That's a little easier for most folks when the bike is in the $1000 - $1500 range.