I haven't been to a spanish one , but the portugese monteria is very similar, sometimes its hetic the moment the dogs are let off, sometimes its not, but it is an amazing experiance even if you shoot nothing.
If you draw a good peg it can be amazing with pigs, deer and mouflon running everywhere and you have to be on the top of your game to make the most of the day as a lot of it is close quarter hunting, very intense
I was on a monteria in feb and it consisted of 30 hunters, 200 dogs and 50 beaters, each hunter was limited to 3 boar per stand , at the final whistle 90 boar and 7 mouflon were grassed, quite an incredible sight.
if you get the chance to go on one then do so, you wont regret it.
only down side is you could have some large calibre bullets wizzing past you.
HH