I'm with the general concensus that you shoudn't punish a group of players because they want to play against the system's "bulit-in" requirement of a "balanced" party. At the same time, the players obviously want to run with the safety off.
Several options immediately come to mind:
* Replace the Heal skill with the Treat Injury skill from d20 Modern. It can be found in the d20 Modern SRD.
* Allow for shorter forays into dungeons, and longer rest periods. A city/wilderness campaign would be much more suited to a non-healer party than dungeon-delving, plus a city would have the benefit of healers built in... at a price.

* Healing fairies/springs, ala Legend of Zelda. In fact, go the distance and have an NPC Pixie Cleric accompany the PCs; it's invisible, it flies, and it's small, so it won't take up much of the PCs attention. Or, have them negotiate and hire a travelling NPC cleric for contract work.
* Encourage someone to take Use Magic Device (Rogues who don't make me giggle).
Or, if all else fails, let the dice fall where they may.