I think I'd take the car back to the dealer and ask for them to properly apply the sand repellant. Bloody shonky work if you ask me!
Seriously, if there's lots of sand there, maybe one of the inner guards is not in the correct place and is allowing sand from the tyres to be thrown into the engine bay. Unless you were smacking the nose into the sand and digging it up, I can't imagine any other way for the sand to get in there.
I'd give the front end a good clean, paying particular attention to the radiator, intercooler (if fitted) and air conditioning condensor.
Edit to add: If you were a little rough on the sand, I'd also cast an eye over the CV boots, make sure nothing gets caught in there and starts chewing away at them. Also check the boots on the steering linkages.