Hi Amanda,
To be honest I think the chances of coming across a snake in the wild are fairly slim - on JY hols you don't really go very far off the beaten track so you should be pretty safe wherever you go! I've been to India and Vietnam/Cambodia with JY and didn't see any in the wild. There was a snake charmer outside the Amber Fort in Jaipur on the India tour, but it would be easy to avoid being anywhere near it! Virtually no wildlife at all on the Vietnam/Cambodia tour.
The nearest I came to seeing a snake in the wild was on the South Africa tour - at Featherbed Wildlife Park, we saw a puff adder from the safety of the jeep. At Blyde River Canyon, I thought I saw a lovely colourful snake underneath a rock, but it was just a lizard!
You could be unlucky and come across one - but that could happen in Britain too! I'd really say the chances are highly unlikely you'd come across one. But to stay safe, don't wander off the pathway wherever you are and you should be just fine.
Hope you go on a fantastic holiday and put all thoughts of snakes out of your mind!
All the best,
Bob