Definitely bring your own tent/sleeping bag - you can drop it off at the luggage trucks with your bags at whichever starting point you are leaving from.

I'm not 100% sure about how it works for people not riding w/a team, but I think once you get into La Grange, you drop your bike off at the bike corral & then go to the luggage area to get your bags. They have areas set up specifically for camping. A piece of advice about the bike corral - pack a plastic grocery bag so that you can cover your seat overnight & it won't be damp in the morning.

Like Aggie says, the fairgrounds are really a lot of fun - I've always stayed there just because it's logistically easier on Sunday morning.

Hope you enjoy your first MS150! If you have any questions, feel free to let me know - this will be my 8th year to ride so I'd be happy to help if I know the answer!