I recently stayed at City24 in San Diego and had a great overall experience. The biggest highlight is the central location. It's close to San Diego International Airport and the cruise port, which may be good or bad, depending on why you are in San Diego. It is convenient but it's also busy and noisy.
The accommodations themselves are spacious and modern, offering plenty of room to relax.. Everything was clean, well-maintained, and thoughtfully laid out.
The building is right next to the freeway, so expect some city noise. I sleep like a brick, so I didn't care.
Despite the busyness, it is convenient, and close to the best parts of San Diego. I enjoyed getting coffee and pastries every morning right up the street near Balboa Park. City24 is definitely worth checking out.