We purchased a City Twinner by Baby Jogger. Same side by side double stroller used at MGM. We have 3 kids under 5 so the double is a must.
As far as folding up for the buses, I was worried about it before we went in September. But seriously, It was no problem at all. The canvas part of the stroller doesn't fold so it seems pretty big but it only weighs 15 lbs and I had no issue getting on or off the buses. Just tried to stay towards the back.