In the Wailea area there are three public access roads all with (limited) free parking. Some are marked with small white signs. Note the three "double lines" leading to the ocean on this map:
http://mauiownercondos.com/images/maps/WaileaP.jpg
A simplier way is self-park free at any Wailea hotel parking lot (it aint exactly kosher though for only beach assess) and tour or eat or drink or buy at the hotel etc. I suggest a drink at the Grand Wailea's lovely impressive Botero bar (beer is a bargain but the mixed drinks are quite expensive and quite weak). Another way is to park at the Shoppes of Wailea and enter there for anything . I suggest lunch or dinner at Longhi's.
MisterNice