We rented a brand new Honda motorbike for $4 a day for the five days that we were in Ubud. For the most part, we just used the bike around town, to lunches and dinners or massages. It was really convenient; we could have walked, but it was quite hot and humid while we were there, generally in the 80's, plus all the roadside pollution from the motorbikes, so traveling by motorbike was much more comfortable. We stayed a little bit far from the center of town, north of Raya Ubud near the Botanical Gardens, so one-way cab fares to and from our villa would have been about $4 as well. We didn't want to take too much risk on the motorbike so the only places that we went outside of central Ubud was to do a little sightseeing at Goa Gajah and Yeh Pulu. Goa Gajah was super crowded with not a lot to see, but we enjoyed Yeh Pulu, There was no one else out there and it was a nice little walk through rice paddies and ducks.
OT, but Lululemon is the best for hot and humid tropical weather. Love the No Limit Tank.
Gas was quite inexpensive as well, $1 for 2 liters. You didn't even need to go to the gas station, just buy them at roadside stands, look out for the yellow liquid in glass liquor bottles.