In reply to ebdon:
I'm not sure about what 'booked up months in advance' amounts to. When I last went a year ago you could take a free bus from outside El Chorro railway station which took you up the winding road and dropped you at the entrance to a short tunnel that's the start of the path, next to a restaurant by the lake. A ~10 minute walk along the winding path, with a boggy swamp on the left and rocky woodland on the right, brought us to a gate and automatic ticket machine, we paid about €9 each for a ticket. People who'd bought entrance in advance had .pdfs of their tickets on their phones, while we just had the things from the machines. I think the people who'd bought in advance were in one queue, and we were in another, so they had some sort of 'priority', but the main point of the queue(s) is just to equip everyone with a hairnet and helmet and to make sure they all understand that they have to go one way (downhill) and that there are sections where everyone has to be spaced out by a metre or two so that they don't overload the walkway structure. The queue moved fast (it wasn't peak season, I guess), like a total of 5 minutes. We had our own helmets so that saved some time, and no need for a hairnet. And then, yeah, you get to walk the gorge, and end up back near the station in El Chorro.
If you'd like to save the expense, it's totally free to walk up from El Chorro along the railway tunnels on the opposite side of the gorge from the Caminito, and there's no need for a helmet. There's plenty of space between the railway tracks and the tunnel walls so that you can be well out of the way of any trains (1 an hour, at most, and always visible and audible a long way in advance). There are security guards in one of the 'exit' kiosks on the path after the end of the actual Caminito, near to a railway bridge, and while they're ostensibly their to prevent anyone from walking up the Caminito the wrong way and without a ticket or helmet, they were also happy to point out to us where we could get down to the railway tracks from the path (a short slope just before the railway bridge, very easily accessible). Helpful and friendly, and absolutely familiar with seeing climbers walking along the railway to the climbing venues on that side of the river.
Post edited at 20:16