Room was very clean, recently renovated, modern, although small. Location is terrific - just a block from the lake, walking distance to everything in town and Via Nassa was gorgeous.
The breakfast was wonderful - staff were terrific, especially with our small children. Staff at the front desk were very helpful and spoke several languages. My only criticism is their dinner recommendation of the Spaghetti Store, which was truly horrible. Besides that, we would certainly stay at the San Carlo when we return to Lugano.