The selection of currency symbols is controlled by your Region setting in System Preferences.
My usual Region setting is Canada, but when I changed that to Philippines, the Philippine Peso became the first choice in the symbols to use for Currency.

Changing my region setting back to Canada made Philippine Peso disappear from the list, but I was still able to select the cell I had applied that format to, Copy Style (option-command-C), then select other cells and Paste Style (option-command-V) to paste the format into the selected cells.

(The symbol did not appear until I entered a number into the newly formatted cells.)
Test done using Numbers 3.6.2 in Mac OS X 10.11.6 El Capitan.
Regrds,
Barry