If what you are talking about is the car seat that turns into a stroller, I would have to say skip it. We used one for my daughter a couple of years ago and hated it. It was really hard to put in the car...the car's seat belt had to go over the car seat (ie. across my DD's lap)...it was really hard to get a good tight fit & in fact, we never really did. DD hated having the seat belt across her since she was used to a Britax seat at home...converting it to a stroller was a real pain, no storage, bad steering...
All around it was a bad experience. If you are renting a car just rent a c ar seat along with it...we have always had wonderful experiences doing that with National. We always rent a car, so I'm not sure what people do on the buses...we just prefer having our own car there because the buses are always so slow & then we have our own stroller everywhere we go.
Hope this helped!