Internationally, I used to live outside Venice, in a town called Vicenza. Pretty good cycling in that area. I live in the SF Bay Area now and it's fantastic. Really close to Oakland and SF you are in area that feels very rural. Lots of wide bike lanes on roads, and there is a big variety in terrain. Lots of low mountains up to about 1500 feet, and plenty of flat too.
also, the winter weather doesn't get severe enough to prevent riding. No snow, and not really all that much rain either.
i know Colorado is another big cycling Mecca but I've never been there so can't comment.