Go get a rental van and when they pull up just block them in. So if they ram the rental van then the insurance will cover it.

Or.. if you know some one with a tow truck just follow them home and steal their van. Hopfully the bike will be inside.

But I would let them grab the bike, follow them home then give them a good wake up call around 4am to their van on fire.

I had the same issues when I lived in an apartment with mexicans. They never tried to steal my shit (from what I know) but they would hang around it and I caught one sitting on it.
I said every racist thing I could to him and he did nothing.

Mexicans are like roaches.