My husband and I foolishly bought the Hop On Hop Off Tour for 48 hours for 18 euros each thinking that it would stop at interesting points in Granada and we would see lovely things. Wrong. The bus does go to the parking lot of the Alhambra (Stop #4), but you do not see the venue, and the Cathedral and Chapel Royale (Stop #1). Otherwise, the ride is long and hot. You have a choice of riding downstairs with no air conditioning (you almost die when the driver stops for 10-15 minutes to pick up other passengers or to chat with one of his friends on the pavement) or upstairs (where the seats are so hot that get your rear end burned through your clothes).
More importantly, the 11 stops on the Tour Bus are not interesting. The bus sits in city traffic at numerous traffic lights and you see modern, albeit somewhat run-down, late 20th Century city buildings. After a while, you feel like a prisoner and desperately want to get off.
Allegedly, admission to a museum (at Stop #6) is included in the price, but the museum is not open on Sundays after 3 p.m. or Mondays.
Contrarily, the cute little City Bus #30 costs 1,20 euro per person and runs from the Cathedral to Alhambra and it is air conditioned.