i am here now. we hired some bikes from 'tommys bikes' in costa teguise, a little shop run by a german couple who are very nice.
i got an old spesh hardrock ht (with v mounts!) but with a comedy collection of parts - xtr combined lh shifter and brake lever (front brake i can't get used to it) seperate rapidfire shifter and a juicy 3 brake on the right (for the rear) xt cranks, v8 pedals, bald schawble tyres, xtr rear mech, nameless carbon bars (really narrow) and a really long stem.
my missus got a trek hardtail with a lower spec collection of random bits including a magura rear brake with braided hose and an unheard of front brake. she brought her own trusty selle italia saddle and vault pedals.
40 euros each for 3 days which i don't think is too bad.
if you got cable operated disk braked bikes you could easily swap the cables over, but you would end up with a lower spec bike - i wanted a bike with half decent forks, but our two have suntours i think, and the wife's bikes ones are nearly seized up. there was a bike with rockshox but it was too big for me.
the people in the shop sold us a really good map, and showed us a few routes on it.
it's a bit hot. you are going to need a camelbak. our bikes came with cages but no bottles. there is no shade at all anywhere.
personally i dont think it is worth bringing your own bike. we are at our own villa so we can keep them overnight locked in the yard, im not sure what you could do with your own bike if you stayed at a hotel - the people at the shop said they do go missing.
go any links to the routes you mentioned?