Much will depend on the individual and how well their own system can cope with unfamiliar foods I still find some foods upset my stomach, although less so than when I first came to Thailand. You will soon know what your system can or can not take so it's up to you how adventurous you want to be. One of the best things about buying food from vendors is that it's cheap, you do try something that you don't like, you've only spent 20 or 30 Baht to find it out,