if going to lvl as prot then gear up as prot. try to keep off set for healing. i did taht even though i hated healing. alot of quest is crap on prot gear that i saw while lvling but the healing gear is pretty good. not to mention i didnt see many plat healers so you also get drops from instances.
if not many good tanks on your sever stay prot dont go holy to get an instance group or two. i tryed that i was 66 with over 600 healing i think it was. but tank sucked they just downed 2nd named in sl. i normaly tank with no cc in there. well they was marking for pally tank hunter trying to trap and rogue sap. needless to say we died like 3 times before even getting to end named room. i had to switch back to prot sell my holy gear to do it. probaly my best thing ever. pally wouldnt use holy shield or aoe at all. anyways if you like healing keep up a set of healing if not dont worry too much about it just keep your prot gear topped up.