Jen, congratulations on getting a trainer. I agree that for interval training, the trainer really makes it easy. One thing you might consider doing is a MAP test. Since you don't yet have a power meter, you can use the trainer and speed as guide, since speed is relative to power on a trainer. After a good warm-up, start at about 15 MPH and add 1 MPH per minute until you can no longer go anymore. If you make it beyond 30 seconds at your highest speed, keep the data. It's a convenient way to see if you are making improvements by performing the test periodically.

I used the Edge to collect data and be able to compare it later.