At your height, a 52 is probably going to be too small. The smaller the frame, the longer the seatpost and the taller the stem needed. The racers who want to get VERY low go for small frames with short stems. I can't imagine you going smaller than a 54cm frame.
Also, if you're concerned about the gearing for hills, pay attention to the small ring in front and the biggest cog in back. I think right now you have a 34t small chain ring with the 26t largest cog. Many of these bikes from the late '80s and early '90s have 39t small rings, and if you go back a few more years the small rings were usually 42t (often with the largest cog of 21t or maybe 24t). Check out some gear-inch calculators to get a feel for which combinations will give you at least the equivalent of what you have now.
Also, get out there and do some test rides. No sense guessing if the Kestrel or any other bikes is a good fit for you, check 'em out. You'll quickly get a feel for what works for you, size wise.