Hello,
While they maybe called Guest Houses, what you are looking for may also depend on the type of money you are willing to spend. If you have a list of a few that you have researched and are interested in, I can tell you the type of area they are end and give you more of an idea of what you are looking for.
If you are here at the end of March, you may be here over Easter Weekend, when the island will be pretty much shut down for 3 of the 4 days that weekend. If you are looking for a laidback, beach, relaxing type of holiday, without the hustle and bustle, this weekend is it (this also means on Good Friday, Easter Sunday and Easter Monday 99.9pct of all shops will be closed including Grocery Stores. Gas Stations with convenience stores will open.
I'll see what I can give you right up front.
Round House in Bathsheba has beautiful views and is secluded and I think there are only 3 rooms in this particular place. It's on top of the Round House Restaurant which serves some really great Flying Fish Sandwiches and BreadFruit Chips (when in season). Its on the East Coast, were the water isn't great for swimming but fantastic for surfing. But it's a great place to relax and unwind.
http://www.roundhousebarbados.com/
Shell on the Sea and Enterprise look nice and are located near "Miami" Beach, on the south coast. Close enough to a nice beach and also not to far from a main bus route to take you into Bridgetown if you want to go.
http://www.barbados.org/apt/shellonthesea/index.htm
Abbeville is on the southcoast just across from Rockley Beach/Accra Beach. It's a renovated old Barbadian Plantation House. Very nice stretch of beach and nice area as well. Again on the main bus line into Bridgetown as well. Canadian Owned and has been around for years (might show it's age). Berts Bar, popular Canadian hangout, has been around for years and is owned by the same gentleman. Not technically a guest house, more a small apartment hotel.