Angela,
I don't really understand your post, because to me if you are going "all out", your heart rate automatically is going to be pretty darn high, if you know what I mean. I think if you want to get technical, yes, there is a range at which your heart rate should stay to be truly interval training and I believe, but am not sure, it is around 90%. Of course, you don't want to have a heart attack, but you really should be huffing and puffing for a little bit. Interval training is suggested to only be done infrequently, atleast for a short duration each session, as the high heart rate and intensity of the training tends to make you more susceptible to injury and overtraining symptoms.
But yeah, if you want to interval train you should be around 90%....which, for most of us, is pretty "all out"....Janice