It can be the suit. There is a HUGE difference in how comfortable a suit is and how easy it can be to put on from 1 suit to another.Rental suits are not the most comfortable wet suits for beginners. If you can get your self a 5mm aqualock.It will go on and easy easily,has alot of stretch and can be as warm or warmer than a rental 7mm suit. Physical fitness and age is another consideration. I picked up on this when OP wrote that she could not get fins on and mentioned the work involved in getting to the beach from parking lot. Perhaps there is a boat that can be used to do the dives from instead of beach entries.make sure your wetsuit fits properly
not being able to move to get on your fins might be due to a too small suit
As to going to a warm location to complete the dives, that can be an option. Nothing wrong with being a warm water island type diver. Yeah it is not going to be as available as local diving,but think about it this way---a local diver may get in maybe in the summer 10 good weekends to dive. Out of those 10 he/she gets to go out 8 times.So for many that turns out to be maybe 16 dives.. A warm water diver on Bonaire can easily do that many in 4 days! So a warm water diver can get more dives in a year than a cold water diver does. Warm island diving can be less expensive as boat fees or as in Bonaire no boat fees are less . No need to own a dry suit that can cost up to $2,000. or more when going island diving, no need to own tanks and maintain them, no need to own 20+ lbs of lead. The list goes on..I would say get certified on a island vacation and if you still feel the need to dive locally get yourself geared up properly in a quality wet suit or dry suit and take the advance course in it so there is supervision on your first cold water dives.