Thanks for your advice! This is exactly the kind of thing I need to be doing

My short hill only takes about 4 munites to climb at 9 MPH - maybe it's 1/4 mile. I have been trying to do it in a harder gear, as it has become pretty easy to spin up in a low gear. I will try to do one munite hard, one munite light.

I also wonder how many times I should do the intervals per week.

Now, there is a mile long rolling hills section right after - would it make sense doing 1 min intervals on that part too?

There is a longer hill in Central park, about 40 munite bike ride away maybe 1/2 a mile - might be worth making the trip.

Now about the psycological part - you are absolutely right. I was the slowest person on the ride, and the group had alread disappeared over the hill by the time I got to it - which was pretty discouraging. I am actually going back to Piermont on Sunday with a much slower group and a very encouraging friend with lots of bike experience. I also am going to take the train to the start point this time instead of the fast 8 mile ride I did to the start point yesterday.

I am taking today off, and plan to do my hill prep Friday and Saturday.