Don't worry about the brand. The important thing is fit. Make sure someone properly fits you. Go for several test rides. Bikes pretty much cost the same and what varies is the component grouping. For example, a Trek with Siora (sp?) may be cheaper than a Cannondale with Tiara (sp?) components, but that's because Siora is the bottim end of the component groupings. Essentially you get what you pay for.
If you want a bargain, look for last years models that still may be around.
(edit - I may have switched the component groupings around)