Appreciate the responses, guys - what you are saying makes sense. With more monitor experience under my belt, I'm sure the rates themselves will have more meaning, and I won't need to rely on the Garmin's Max% or zones. After a week and a half, I already know some rates that are clearly transition points. I just don't know from what to what, so it's hard to relate what I'm doing to the training guides. As I've said, I'm a total newb that wants to get fitter and faster.
Carbon... did you determine recovery zone 2 using perceived effort, or is that something determined by test?
I'm seriously considering a metabolic test to get my initial thresholds nailed down. The rehab place that does them here had a drawing at the Tour de Scottsdale, but alas I didn't win.