There's no need to go out of your way to get this one. After leaving Prision "El Corazon," you will have everything you need. Simply continue through to Agave Field, and Casa de Juan can be entered through the Dead World. As a bonus, you'll have Pollo Slide and can get the heart container in the basement without having to come back for it.
If you'd like to get it as soon as possible, however, this is first obtainable after you get the Dimension Swap from the Badlands. Fast travel back to Los Manglares, then head left to Agave Field, swapping back to the Dead World.