Two geo data sources from Mexico have been made usable in TransDEM 2.2:
INEGI WMS Information
(in Spanish) Servicio Web de información geográficaCoverage and detail vary.
Access data for the WMS is part of the sample configurations, downloadable from my website. The setup includes a layer preselection.
An explicit custom WMS protocol version parameter is also set. This parameter, new in TransDEM 2.2, must be provided to obtain readable results. This WMS has no default, and the default in TransDEM will not be understood by the server.
INEGI Seamless Server DEM These DEMs (Modelo Digital de Elevación, MDE) are terrestrial and have been derived from 1:50,000 topo maps. Nominal resolution is 1 arc sec. I have checked for Barranca del Cobre (Copper Canyon). No voids here, quite a contrast to SRTM.
Sistema de Descarga del Continuo de Elevaciones Mexicano.
The server can be slow at times.
Data format is ESRI .bil. You will need TransDEM 2.2 to read it.