My daughter is 19.5, and I'd only be comfortable with her staying onsite- and I am a BIG advocate of staying offsite. If you are a Disney resort guest, you can take Magical Express from MCO airport to your resort, and back again at the end of your visit. While you are staying at Disney, you can use the bus and boat system to get you to any Disney park, resort, and Downtown Disney. As has been mentioned, rental cars are expensive, and if the driver is under 25 yo, there's a huge additional charge, and then there's the cost of insurance and parking at the Disney parks (currently $14 a day). Yes, some offsite hotels offer shuttle service to the parks, but it's often shared with other hotels, increasing transportation time. You also have to adhere to the set schedule... they really won't care if you want to go to/leave a park now, you have to wait for the next scheduled shuttle. We did a shuttle for one day, years ago, andthen rented a car. Offsite shuttles are a HUGE hassle. Just the convenience and additional cost of transportation makes it worth it for you to stay onsite at a Disney resort.
Stay at a value resort, if you don't mind double beds. (two to a room, each bed holds 2 adults but is only about 4' wide... not sure how that measures up for you). These rooms have private (small) bathrooms and each room also has a phone, TV, and small refrigerator. If you want to get some food for your room (breakfast stuff, snacks, etc) you can have an order delivered via Garden Grocer, or you could take a cab to the nearest Publix supermarket or
Walmart (don't go to Goodings, they are SO expensive). Your resort will have a good food court, several swimming pools, and an arcade area. The value resorts are served by the Disney bus system. They are a great deal if you watch for specials and book "room only," getting your own park tickets and buying your food out of pocket. Having said that, you also should check into specials for non-USA residents, as sometimes the tickets are a much better deal than those you could buy here. You might want to check with a
Disney travel agent (
Dreams Unlimited is great- see top of page for a link) to see what the best on-site deal would be.
When we went to Universal to see Harry Potter, Dreams Unlimited was running a special that included tickets and transportation from Disney hotels. I don't think that kind of thing is still available, but a
travel agency such as DU would know the best way to get bus/cab fare to the other theme parks. It's probably even possible to use the city bus system, but I don't know where you'd pick that up.
PS- Just asked DD and she said if it was just her and friends traveling, there's NO WAY she'd stay offsite!