This doesn't have to do anything with language or cultural differences. It is the frustration of people demanding to have wifi access or sneak in our breakfast room and eat full breakfast without us offering.
I am sure there might be a business owner in this forum. What would you do if you were in my situation?
I would build a marketing plan that has the goal to turn more of these visitors to my business into paying customers. The first step would be to find out how many of them are already paying customers. I would make an effort to find out how many room nights I am actually getting from Tesla owners. If you don’t want to ask each guest at registration then I would take PlusEV’s point and simply have someone survey the parking lot each morning for Teslas. Keep track of this data!
I would also try to find out how many Tesla drivers stop at my location every day as this defines my potential market. I assume that Tesla will not share that information with you? I would take down the sign warning users against bad behavior and replace it with one welcoming them and inviting them to come in for a cup of coffee or lemonade while their car is charging. Just show your Tesla key at the desk! Again, keep track of this data!
OK, now that I have a way to capture data about the size of my potential market, I need to figure out how to turn them into paying customers. Right now, I have only one product to sell to this market: overnight stays at the hotel. Given that Ozona isn't a destination for most of these visitors, I'm limited in how many I can actually serve. I need to figure out what else I can sell to people who will only be on my property for ~one hour. Food and drink seem the most obvious choices. I do not know if you're restricted in this area by your local permits or franchise agreement in any way but offering these types of consumables would be my priority. The nice part is that this is a captive audience and my prices can be higher than local options even though this is a smaller revenue stream it should be very profitable.
Once I have enough of a sample size that I feel comfortable with my estimate of the size of the audience and I am ready to start selling something to these visitors, I would replace the sign offering free coffee/lemonade with one inviting people to come inside the air-conditioned lobby and see my selection of food and drinks available.
That's a plan to convert transient visitors into paying customers. I would also consider ways to incentivize more Tesla owners to choose to plan their long-distance trip so that they spend the night at my hotel versus the hotels at/around other superchargers. Simply building the reputation as a welcoming place for this market would help. I'd put in place a 'Tesla rate' with a nominal discount over the normal rate and see if that moves the needle from my baseline count of Tesla room nights.
I would install a trash can out near the charger to incentivize users from littering. It is an expense I shouldn’t need to incur as people should know better but clearly some of them don’t. Keeping my property clean and appealing is more than worth the cost.
Ultimately, I would realize that I need to do more to market my services to this audience than a passive approach of waiting for a (small?) percentage of them to check in for the night. It's an entrepreneurial challenge to turn this negative situation into a positive one but the return should be worth it.
Good luck to you.