It really depends what you wanna do for your holiday and who're going with you.
A lot of my friends travelled to Desaru and Malacca as their first trips to test water. So that they have the energy to handle if their kids get cranky. Their kids were all 9mths when they tried.
My hubby's cousin however has been jetting all over since their son turned 3 mths. They've already been to HK, Korea, Bangkok, Vietnam and malaysia. Their son is now 1 years old and all their trip the grand parents also followed so they had an extra pair of hands.