How about at step 1, "Listen dude, I don't want to talk to anybody, I don't want to walk with anybody, I don't want your number, I don't want your weed, and I don't like your face!
Now I'm going to turn around and hopefully be walking off by myself, I'm hoping like, you and me, we don't have a disagreement on this issue, and things escalate and potentially get ugly real fast, know what I mean, Vern?
Then turn around walking away, but be looking out of the corner of your eye at him...
Then if he continues after you, duck in a store and tell them to call the cops, or if you've sized him up good and you're confident you can make good on making things get ugly for him real fast, have at it, today turned out to be your lucky day!!! And fresh from Monica's on top of it!! It'll be the height of your vacation story...
If any cops ask you what happened, hand out 20 mil to each of them and tell them he was trying to steal from the cop's widows and orphans fund and you want the money to go straight to them so they can deposit your donation themselves...
They'll thank you, you'll be on your way, a great story to tell, you had the fun of delivering a comeuppance to an obnoxious jackass, the fun was well worth the money, and some widows and orphans eat for a week thanks to you...