To put them off the scent: Estoy de novia = I’ve got a boyfriend
For seriously cheesy or cheeky remarks: Me estás cargando?! = Are kidding me!?
If someone is really chatting you up: Qué piropo más grasa! = That is a such a cheesy chat up line!
Fancy meeting up with them in the future?: Te parece si nos juntamos otro día? Do you want to meet up some day?