In that case I would just call the hotel. Maybe email them in advance explaining that you will be doing so and at what time, and they can ensure that there is an English-speaking employee available.

My previous suggestion would still be my preferred method though, if available. I've booked hundreds of local hotels all over the world this way, often the same day I was planning to arrive. It makes the transmission of the necessary details to secure the booking the responsibility of the agent, rather than you.