Also check out the mountain page for the mountains you have in mind. Cheers.

http://www.cumbre7.com.mx/

Check this link. Page is for Ruben Garcia. We have climbed w/ him in Mexico and he organized our trip in Equador as we speak no spanish (our picture on the English site on his web page) He is also referenced in Secor Mexico vocano book. He is super w/ logistics, knows Mexican volcaonoes like the back of his hand and is generally a first class person. His prices are also much less for private guiding than for groups w/ American companies. You may have some difficulty w/ understanding his written communications but he speaks good english so don't worry about that when you get there.