I assume Telemundo's target market is not Spanish-only speakers, but rather those who do speak English well enough to get a job that pays well even though Spanish is still their first language. Any Spanish-only speakers are welcome to inflate the viewership numbers but advertisers are probably buying based on the number of dual-language viewers (for disposable income).

I'm assuming Telemundo etc make money but don't know how profitable it is to lock out the much-larger English-speaker market.

I can think of two potentially unique problems to porn:

1. The cost of doing an acceptable dub into Spanish, while cheap, might be a big cost in the budget of most porn. It depends on how crappy a result the market lets you get away with. If dubbing only sells an extra 300 units how much do you spend on it? And more likely, what if you can't see any difference in sales between dubbed and standard units? Finally, once you know how much dubbing will cost, can you put the money into some other aspect of production and help sales even more (i.e., hire more-expensive talent etc)?

(the last point is that when budget is increased you start over on how to spend it all: if you get to spend an extra $1000 the question is how you now best invest the total; it's not the case you blindly assume the base budget can't be improved on)

2. It might be a moot issue entirely if Spanish-speakers watch porn the way English-speakers do: with the sound turned off.

There have been a few Spanish-language releases such as Sineplex's Chica Chico last fall (US porn talent but moaning in Spanish). I don't know if they dubbed an English language track onto it.