So some loops are very far from everything, and some are not.
Here is a map: http://www.wdwinfo.com/maps/FWMap.pdf
Here is a list of which sites are classified as what: http://www.fortfiends.net/topic/16887-loopsite-info-page-backup/
That fort fiends site is fabulous as well, and the community is great. They completely understand that sometimes it is hard to find info on the fort so do a great job of having a place specifically for that.
Anyway - back to your question. I'm assuming you have your own vehicle in addition to your motor home since you mentioned driving.... If you do not have a car with you, I would say, yes - rent a golf cart.... although depending on what you find renting a car for the week might be cheaper
My husband and I stayed on the 2000 loop because we have a teenie little teardrop trailer (it is a pop-up and tent loop). So we were at the mercy of transport. I was very pleased, though. We typically did one of three things:
1) Took the FW busses to the Outpost (for everything but MK) or the Settlement Depot (for ferries to MK, the lagoon resorts and also if you are going to see HDR) and then hopped on WDW transportation accordingly.
2) Drove to the Outpost - where you can park for the day without any troubles - and then took the WDW busses (what we did most often).
3) Drove to the park - We only did this on our Animal Kingdom day because it was our last day; we needed to Rope Drop, and I wanted a little extra sleep - so didn't want to have to wake up earlier to allow for transportation time. I just wanted to get in the car and go.
We were totally fine without a golf cart. However, we simply stayed at FW and basically just went to the parks. IF you are planning on going to the pool a lot, taking part in some of the recreation activities, going to a lot of the evening events... basically if you are going to do a lot of traveling around in FW other than just getting to and from the parks.... you may want one if you don't like driving your car on vacation (some people think it kills the magic). There are parts of FW that are walkable, but as you can see from the map it kind of depends on where your site is.