b and b in Prague

You put your question under Czech Republic Reviews. It says: Share hotel & restaurant reviews. But you are not sharing. I think your question would be better suited under Czech Republic. You want to be near central Prague. Rick Steves recommends 2 pensions in his book Prague & the Czech Republic (me too): Pension Vetrnik, Guest House Lida. Both are easily reachable from the center by a short ride on public transport.

I stayed a Lida in 2012, and it was wonderful. The two brothers who run the place speak excellent English and are enthusiastic about Prague. Right after I arrived, the brother who was running the place that day (Jan, I think) took me into the breakfast room and opened a big notebook with pictures, maps, and other information about Prague, showed me what to see and how to get around on the public transit. He gave me a good recommendation for a restaurant within walking distance of the guest house. The next morning there were lots of people with blue books in the breakfast room.

I only know one, but it was excellent, very centrally located, sort of between Charles Bridge and the Town Square, highly reviewed, and of modest cost: Green Garland Pension.

I think you are really limiting yourself with just B&B or pensions. Loads of reasonably priced places throughout the city that would serve you well. Look at booking.com for an idea of what is available.