Yes a cory and pleco wil be fine with the group I suggested. As some others have said, the kissers will not be able to reach their proper potential in a 20, so as long as the tank really is only for a short time, and that you buy them small, they should be fine.
You may want to replace the kissers with a pair of dwarf gouramis, they are not expensive, colorful, peaceful, and wom't out grow the tank, coolie loaches would also be a nice addition.