We chose San Carlos because of its proximity to the Zona Viva (walking distance, but I would taxi at night). It appears charming from the outside, and inside it is decorated impeccably with antiques, cozy sitting areas, as well as a main bar, restaurant, pool, and front desk area that sells some drinks and toiletries.
However, there were some basic problems with guest services, which I soon found out after checking in. First, they could not arrange any tours for us. Incredibly, they told us they had no concierge service or any kind, which I find odd for a hotel that charges $98 usd/night for a standard room and is located in a prime tourist area.
They also advertise in the hotel about spa services. When we inquired about booking a massage, they informed us since we were not staying in one of the "executive" suites, we could not take advantage of the spa services. Are you kidding me? I have to pay $40 usd more a night for my money to be good enough for a massage? This kind of class system exists in one of the sitting rooms, as well, where a sign prominently announces "For our Executive Guests Only." Way to alienate a portion of your guests Hotel San Carlos.
Next, we asked if we could buy some bottled water. Sorry, fresh out. Wow! All in all, we found the front desk incapable of handling any basic request. The rest of the staff in the restaurant and bar were incredibly friendly, helpful, and eager to please. The food was great and the drinks too.
I used the pool one sunny afternoon, and found the rod iron pool furniture (chairs only, no recliners) to be extremely uncomfortable, with only small cushions, which didn't absorb water very well after a dip in the pool. Speaking of which, no towels for the guests either.
Our standard room was quite large, but the bed was way too soft, the shower didn't drain properly, you had to hold the handle on the toilet down the whole time to get it to flush, and there was no where in the shower to put your shampoo, etc. except on the floor - minor annoyance but worth noting.
We had room 3, which faces Avenida Reforma, so there was traffic noise, as well as police style spot lights they shine on the building (4 in all) for security, which makes it appear as if it is day time out. Luckily, they have good blinds to block it out, but leaving your blinds open at night to enjoy a view outside is out of the question. If traffic noise bothers you, they have plenty of rooms available at the back of the hotel.
Speaking of security, that was very good, with a guard at the main gate (although we found him dozing one morning on our way out). I wanted to like this hotel very much, but there was just too many little things wrong, and their treatment of standard room guests is very counter-productive and archaic.