I know it is frustrating wanting to help and having to pay almost as much as you would for a full holiday to so do. I found this frustrating when I was looking into it – I tried to remember that if an organization is going to pay my way somewhere, then that is money diverted from the project. If you really want to help, it shouldn’t matter where you volunteer – so look in your own backyard – most cities have many organizations which are always short of volunteers! If you want to go to a different country because it would be neat to help AND see something new, then be prepared to pay for seeing something new. 

I’m sure if you wait until the end of hurricane season you will find lots of opportunities to volunteer in spanish speaking area, even if its only Miami. 
 
Otherwise, try WWOOFing. 

 
you can do mine-clearing in Afghanistan on a budget

Keep trying.  Going somewhere to help isn’t supposed to be a free/cheap vacation.  Most organizations that need volunteers do so because they don’t have the money to hire someone.  Don’t expect any deals though.

Side story.
I tried to volunteer with the Red Cross to help in India after the tsunami.  The RC guy made some pitch about them wanting water purification experts, etc.  I was thinking that I didn’t need training to help clean up.  Pretty frustrating since I told him I had a ticket to go, etc.  Didn’t want free help I guess.