I would not suggest falling in love with someone you're not sure you're compatible with unless the tickling / foot thing is really not very important to you.  At worst,  you end up frustrated,  dissatisfied,  maybe heartbroken.  At best,  you wasted time with someone when you could have been having fun with someone else.
		
		
	 
I mean, maybe, I guess, sort of..
You do generally need to carry it past the point of the first or second encounter.
When you've hit three or four dates and you've got a connection and are in sort of "relationship prep mode", and those smitten feelings are starting to take hold..
..yeah, I'd say drop it then.
Unless you've had success telling guys when they come to buy you a drink that you like being tickled..
Guy: Hey yo! What you drinkin'?
Girl: Amaretto Sour. Want to hear about my fetish?
..in which case you've got far more game than me 
🙂
I've always had it sort of naturally play out early on, I'm trying to take what happens naturally without much of a plan and put it into words.
There comes that time where you're starting to cuddle and talk about shit (..and get into poke/tickle fights 
*hint*)..where it becomes a lot easier to slip in that this is something important to you and have it received in a much warmer, understanding way.
If it blows up in your face, then, well, you've lost a friend with benefits but that's about it. Swallow the lump in your throat and drive on.
If it doesn't, you can move on into solidifying the relationship.
That's how I've personally found the most success.