They have not put up their logo on the outside of the building. I did try and go in the commercial building their office is located in. However, there is a security guard at the front counter that will not let you in unless the company has scheduled a meeting with the front desk.
Go to this page to see the layout of the offices located inside the commercial building. You will see ESP's office space. Per the 10-k, they're paying approx $11,000 in rent per month, which sounds about right for this location.
Now, if you look closely, in the top left corner of this picture it says, "American Charter Title". Locate them on the map relative to ESPs office and you'll notice ESP is in the top far right of the office building. I went here for drinks 2 weeks ago but their logo was not hung on the outside of the building.