Most of PdP is totally flat. Areas outside the bypass do have slopes and in Gommar area further out they become steep (but you won't be going there IMO).
I always recommend staying "inside" the area within the bypass anyway. And that's all flat. The link below may help.
http://www.puertopollensa.com/maps/pdfs/portdepollenca.pdf
The old town does have slopes behind the church square, but you should be ok as far as the lovely church square. (And don't get worried if you learn about the 412 steps up the hill in Pollenca old town; you won't be doing those but you could stand at the bottom and look upwards).
PdP is great for restaurants - all types, all price ranges. Shops as well, but restos is its big pluspoint.
If you tell us what accommodation is on your shortlist, we can advise better about proximity to restos etc.