This famous horchatería proposes some coffee-based drinks such as "sospir" (iced coffee with horchata), cortado coffee with horchata instead of milk, etc. I like these!

In addition to the classic fartons for horchata, they also have really nice pastries and cakes such as orange sponge which is super yummy.

There is free wi-fi sponsored by the town hall, but this is an open air space (it is, after all, in a market), and although they have heaters in winter, the tables are not very comfortable so I would not call it a laptop friendly place. There are often pushy beggars roaming around so you'd better keep an eye on your stuff. I would advise you to find another place to work from. Just drink the horchata and go elsewhere.