From what I've read, iMovie does not handle AVCHD sources at all -- such as those from HD cameras like the Canon HV20. iMovie only works well with standard definition DV footage. You'd have to use Final Cut Express, the most current version, for HD editing. I no longer have an Intel MacBook to test with.
Honestly, I'd say Premiere Elements is better than iMovie, especially comparing the current versions of each. I'm not anti-Mac at all, but I find the iLife family of products (iMovie, iDVD, iPhoto, etc) to be extremely crappy software. It's basic software with a few whiz-bang silly features, but totally lacks important features for quality output.
If you're shooting HD videos, there is also the question of how you plan to distribute or even view the content. You'll need to down-scale to DVD, buy into expensive Blu-ray burning/authoring technology, or simply watch on the computer only (or a computer connected to a television). The camera was only the first step.
If you're happy with DV, and you understand the workflow, that might be a better place for you.
When it comes to DV cameras, I highly suggest the Canon DV systems, as those DiGiC processors do very well at white balance and low light situations. My favorite line is
the Canon ZR series (follow link to see models currently for sale at Amazon.com), and those cameras are available for a song now, since it's "old technology" to the purist crowd. If I needed a DV camera right now, I'd look at
the Canon ZR950 sold by Adorama at Amazon for all of $219 shipped free, tax-free.
Then again, if you're really wanting HD shooting, new tech,
the Canon Vixia HF200 is only $599, best price. Still above the budget, however.
Whatever you do, buy online from a trusted dealer ONLY for the best price.
Amazon.com is trusted, as is
Adorama and
B&H. Those no-name stores, especially New York or New Jersey ones, are usually scams. You can buy in a local store too, but you pay $50+ mark-up for that convenience, and the salesmen love to hound you with unnecessary crap and warranties -- often lying to you in the process (Best Buy is notoriously full of idiots).