Hey A,
Good luck with the ankle! Strange that the ER never told you it was broken?
Regarding trainers - they pretty much all do the same thing. I would recommend getting a trainer that has a resistance knob you can adjust while riding to somewhat simulate hills. I have a couple teammates who have that option and it beats having to stop and get off the bike to adjust it. Also - and more importantly - get some really good cycling dvd's. Because your movement is limited it's hard to stay on the trainer for long. I tried last winter to pedal indoors - and only had 3 days on the trainer before I was back outside battling the elements.
Another option to a trainer are rollers. I found a pair at Supergo for $100 and it's a great way to simulate road riding. It will help you with balance and bike handling. And it's not as boring as sitting on a trainer. But that's my personal opinion. And if you are still recovering from a broken ankle then I'd hold off on the rollers - you tend to fall at first due to the learning curve.
Cheers!
Jen