bike rental or buying a bike plus other questions...

We are staying in ixtapa from Jan-Mar and we're looking to bike every day. Anyone know of good bike places to rent or to buy bikes - mountain bikes as we plan to do the cyclepista and some dirt roads as well?

Also, any good places to rent cars and scooters as well?

we would like to volunteer some time in alcopolco and area as it I heard it got hit pretty badly again. Is there a place we can sign up to volunteer to help out some place?

and, is there a cheap way to get there?
what is the cheapest way to get to Oxxaca and Hautalco ? bus or fly or rent a car... I think its 15 hours to get there?

thanks in advance, looking forward to heading back to ixtapa.