I have gotten back into riding in a big way this year. A number of months ago I got a Garmin edge 305HR and love it for its geekiness. But I also find it a source of frustration.
With my new son being born 3 months ago, I am basically starting over again. I would love to HR train, but with my local routes it is kind of pointless.
The roads I ride around my house are very hilly. Going up some of them, even in the granny gear basically spikes my HR. I have natural hill repeats
So basically I have determined I just have to give up for now and just ride. Spike my HR on the way up, recover on the way down. Hopefully after some more time getting back into shape I will get my fitness to the point that I can start doing more targetted training.
Sound smart? I am guessing that maybe while not ideal, riding hills all the time will still certainly work at getting me into shape (not completely burning myself out). I mean plenty of of other people live in areas that only give them a certain type of terrain and the do fine.
I have the same issue here too, the routes around my house are extremely hilly. I rode them hard and often for several months and then rode one of the local rail trail (read; FLAT!) for about 75 miles and it just tore me up.
I have determined that for me it's best to mix it up as much as possible. Hills are great for speed and climbing, but it's really hard to do tempo work. So I schlep over to the rail trail at least twice a month and ride 75-100 miles at a time.