During our holiday in Spain, we travelled to Gibraltar on a couple of days. The weather was not very good on either visit, even though the rest of the country basked in glorious sunshine. Because our second visit was on Easter Sunday, a lot of Gibraltar was shut, including the cable car which we were going to use. Hovever, we took a taxi tour of the rock which was the same price as the cable car but did take us to see all the sights. This would have taken ages if we had had to walk around.
Conclusion: Take the taxi, it's worth it!