I'm looking forward to La Hija de Frankenstein, I have that one on its way to me.  And thanks to Torgaman again for the lowdown on the other lucha libre movies. 
 Here are some of the Santo movies I've been watching over the last couple of weeks with some random opinions:

SANTO EN EL TESORO DE DRACULA - This one's really pretty good, and even kind of works as a real DRACULA adaptation.  Of course, there's the wrestling and time machine added, but that's as least as legit an addition to Stoker as the weird Gary Oldman beehive hairdo. I find it fairly amazing they actually made a the nude version of this, since it's otherwise fairly kid-oriented like the other Santo movies.

ATACAN LAS BRUJAS - fun and cheap even for a Santo movie, but I thought the old mansion setting was pretty effective, and the HORROR HOTEL footage out of the middle of nowhere had me thinking I was hallucinating just like the guy in the movie.  Maybe not the top tier but not bad.

EL HACHA DIABOLICA - Good pacing in this one and the black-hooded ax-wielding villain really keys things up.  If you're really a dirty fighter, why  not just bring an axe to the wrestling ring.  I liked this one a lot.

SANTO EN LA VENGANZA DE LA MOMIA - If you don't like the Scooby-Doo ending, beware, but it's got some pretty neat touches.  Unlike other mummy movies where the dusty one pretty much ups and leaves and attacks people when they're not looking, in this one he's just lying around a lot while people don't believe the big lump of jerky is actually capable of attacking until it's too late. 

SAMSON IN THE WAX MUSEUM - watched the K. Gordon Murray dub of this and what can I say, I'm a sucker for a good wax museum movie.  Liked it.

EL MUNDO DE LOS MUERTOS - I watched this one unsubbed, so I couldn't necessarily follow all of the plot details but really liked the visuals in this one.  As one Amazon reviewer points out, it has a DARK SHADOWS kind of vibe with reincarnation/time travel themes and that late-sixties kind of "look".  Would like to see an English-friendly version of this one.