Making photos inside the caves is now possible. But remember you're not allowed to take photos of you sitting next to a Buddha statue, or having your back to him. This is the reason photography was banned for some time as a female tourist had herself photographed on the lap of a Buddha statue (this is scandalous for Buddhists)
Remember shoes have to be reoved as this is a sacred place and also cover shoulders and knees.
And there is an admission fee to the site.
In Dambulla there are officially three things to see: the Golden Temple, the Buddhist museum and the Rock Temples. All three erquire separate tickets, but only one is really worth your time and money: the rock temples. The price is 500 rupess (source: november 2004) and the tickets are to be bought opposite thhe museum, as there is no opportunity to buy them once you reach the rock temples