Peso notes come in 20 ($1.40 current rate) 50 ($3.50), 100 ($7.00) , 500 ($35.00) and 1000 ($70.00).
I seem to remember a 200 ($14.00) peso note as well, but was only able to get 50, 100 and 500 from the exchange place I used this year. I have a handful of coins left over from a previous trip but I forget what denomination they are.
We found that the 20s and 50s were good for tips. The bartenders are always good for breaking large bills into smaller ones.