Most, if not all, of the rental vendors should have something that is "portable" (meaning you can take it apart, and put it in the trunk or cargo area of a automobile).
As far as *who* to rent from, that's really subjective. I would look at the most commonly mentioned vendors here (currently seems to be
Buena Vista, Walker, Apple and Yellow) and I always reached out via phone to any company I was considering renting from. I would ask them questions to see how they treated their customers, and what their policies were, for example, if the rental unit had a problem after the office was closed for the night. They will try to sell you "insurance" - ask each vendor specifically what it covers (and ask to see the policy beforehand so that you have time to review it thoroughly - and then ask your insurance agent that supplies your Homeowner's and/or Auto insurance policy(s) if you would be duplicating any coverage prior to signing up) Ask them any questions you might have *now* on the phone. You can typically tell a lot about a company by the way they answer (or don't!) these kind of questions. And remember that price and quality are not always equal; when I was a purchasing agent, I learned very quickly that the highest priced vendor and the lowest priced vendor were often not the best choice; the former is often overpriced and ripping you off, and the latter is usually cutting corners and offering an inferior product or service. You might pay a bit more for the quote that falls in the middle, but it's also more likely to be a realistic quote and a solid offering.
Although it's been a few years since I rented from an external vendor (like some other folks around here, I have my own
ECV that I travel with), here's a few tips that might help - regardless of the vendor!
First of all - and I can't stress this enough -
charge the battery overnight, every night. A rental ECV should be able to go all day at WDW if it is properly and fully charged overnight. The exception to this is if a customer needs a larger size (bariatric) unit, and tries to "get by" with an undersized unit, the battery will drain faster because it is under a greater strain than it is designed for. Make sure the ECV you rent is the right size for you!
It's important to have the office hours & availability of your mobility vendor at hand. (Prior to owning my own ECV, I would make an address book or contacts entry in my phone for any mobility vendor I would rent from, so that I could access the number easily. In the "Notes" area, I would include information like office hours, and ask them about emergency after hours information.)
Do take the time to ask the vendor what their current after-hours policy is regarding an emergency - like if the unit stops working altogether (but the battery was charged) or if the battery won't hold a charge at all. Most of the time you will know if there is a problem well before they close the office for the day, but rarely, an ECV will fail later in the evening. If it should happen, find a Cast Member, tell them you need assistance (you may have to ask for a Manager to come help) and then leave a message for the vendor, and follow any emergency instructions they have given you.
Some people will confuse the *cosmetic condition* of the
scooter with it's ability to perform. Rental scooters do receive a lot of abuse at the hands of either new users, or careless users ("It's not mine, so I don't care!") and often this shows in the cosmetic condition of the scooter - scuffs, scrapes, broken plastic covers, ripped seats, etc. As long as the unit *performs* - meaning it runs all day on a full charge, and gets you around safely - don't worry about how it looks.
Buy a cheap, colorful bandana, or a roll of brightly colored/patterned grosgrain ribbon from either Walmart or Hobby Lobby (they both sell ribbon and bandanas - pick something you like!) and tie it somewhere on the ECV that is visible. It will help distinguish your rental from a sea of identical rental units outside of rides, attractions, dining, etc. The more you decorate your rental, the easier it will be to spot quickly!
Last, but not least, snap a couple of photos of the ECV when it is dropped off (both sides of the unit) and keep your paperwork safe somewhere besides the scooter. Just like when you rent a car, you want to be able to prove the condition the unit was in when it was delivered to you. Make sure that the battery is fully charged when it is dropped off (it should be) and that the charger is with the unit.
And go have fun!