Soon you will come to a T intersection. The Hotel is to the left, the Penzion to the right.
At www.mostov.cz you can click on Online Rezervace and make reservations at the Hotel but I did not make my reservation this way. I made my reservation at the Penzion but no one was there when I arrived so I drove to the Hotel and fortunately a room was available for 50 Euros/night. At first I spoke to them in a mix of Czech and German but I knew little of either language. Also, I wrote out some sentences. When finally I registered for a room and presented my passport the man said in plain English Ah, you are American. In their restaurant they do have an English menu. All this said, the English spoken at the Hotel is minimal and probably limited to 1 or 2 of the staff.
The web page you get by clicking Online Rezervace. You might also try: http://www.mostov.cz/aj/kontakty.htm
I now email the owner of the Penzion online at: firstname.lastname@example.org You can write in English and the proprietor, Radek Novotný, uses Google Translate to understand what you write. The cost/night he quoted to me was 14 Euro/night which is very cheap!
If you google for Penzion U Zámku you may find other ways to contact Radek.
Here are some photos I took while waiting at the Penzion.
Hotel Mlýn is the building in back on the left. This is where my room was. Mlýn means mill so it seems this building was originally a mill. Ž amek possibly refers to a lock on the river but I did not see such a structure. It may mean castle. Penzion U Ž amku means Bed and Breakfast at the Lock or at the Castle.