This is a lovely hostal, in a quiet street, near the centre of the city. The couple who run it speak good English (the husband particularly, as he is an engineer who once lived and worked in Canada) and are genuinely friendly and warm.
Breakfast in the morning, in the little patio at the back, was the best I had in 4 weeks in Cuba.
The room was comfortable and up to the standards of a European family-run hotel.
Cienfuegos is affected by lengthy power cuts, but the hostal is not. As a rule, the power is on all the time. That is because the hostal is near a hospital. I still recommend having a portable, rechargeable lamp with you: the owner helped me to buy one in town (4,000 Cuban pesos).
Internet access (WiFi) is a bit patchy, because the relay tower lies in an area that is affected by power cuts, but I still managed to check my emails and the news on my smartphone daily (usually, the window of opportunity was the morning, before going out).
Overall, an excellent 'casa particular', with the owners who make you feel welcome and are very helpful.