The Most Uncomfortable (Noise-Wise) Hotel Room I've Ever Had
I just returned from my first (and probably last) stay at the Hampton Inn San Diego downtown. I was in town for Comic-Con and this was one of the approved convention hotels. I'm a loyal Hilton hotels fan and this Hampton Inn had the classic, comfortable rooms I've come to expect from this brand as well as the stellar service, but the HUGE problem with this hotel is the train noise -- and you can't change the location. 
I am NOT a light sleeper by any means, but I feel like I must echo this point: the trains and the track crossing gate are OBNOXIOUSLY LOUD and will KEEP YOU AWAKE ALL THROUGH THE NIGHT. When I checked in, I specifically requested a room "away from the train tracks." The front desk clerk was friendly and told me that she indeed had me in a room that was far from the tracks. I was so happy about that and the room was on the supposed "quiet side" of the hotel. If my room was on the quiet side, I'd hate to see what a room on the loud side would be like! It was the absolutely most uncomfortable (noise-wise) hotel room I've ever had anywhere in the world.
The problem is that the hotel is feet away from the city trolley track which also serves Amtrak passenger trains AND huge freight trains 24 hours a day. There is a train crossing directly behind the property so every time a trolley or train blows by, the cacophonous "clang clang clang clang clang" and flashing red lights make quite a ruckus. Once the city trolley stops running, there's a little peace a quiet...until you are awakened multiple times a night at 2 am or 3 am or 4 am by CONSTANT LOUD TRAIN HORNS blowing and blowing and blowing, followed by the startling horror that perhaps the Hogwarts Express is rumbling DIRECTLY THROUGH YOUR HOTEL ROOM. It is HORRIBLE. I don't care if there's going to be a quiet zone to silence the horns (which the date of effect apparently keeps changing), that won't stop the dang crossing lights and gate from clanging whenever a train passes by. It is miserable and I did not get a good night's sleep for the entire 3 nights I stayed at this property. The train horns are absolutely obnoxious, and a big part of a hotel is location, location, location.
As a side note, at least the trolley station is convenient and for $5 you can ride all day long! There's not much around the hotel but there is a Mexican restaurant next door and a Rite Aid a block away. The Convention Center was a bit farther than I expected and took about 25 minutes to walk there. After a long convention day, that was a bit too much for my feet! The convention shuttle bus was easy and took a little less time to use. Also, our shuttle line was never that crowded as compared to the other convention shuttles. This would be a great hotel if you were taking a cruise since the cruise ship terminal is within very close walking distance. (But don't expect to get much rest as a result of the train tracks).
The rooms are clean, spacious and comfortable. The bathroom had one sink with a large vanity and a shower only (no tub). The carpet was clean and the decor was modern and updated. The hotel is a U-shape that overlooks an internal concrete courtyard so be sure to keep your draperies closed for privacy -- I could clearly see into the rooms across the courtyard. Complimentary internet access was nice, as was the free breakfast in the morning (I didn't eat breakfast but I did check it out to see what was served -- your usual carb-heavy stuff: waffles, toast, cereal, coffee, juice). I would've liked it if the rooms had in-room refrigerators but that was no big deal. I loved that my room was cool and the a/c worked properly. There was no annoying regulator or motion sensor on the a/c temperature so we could keep it as cold as we wanted. I really hate those hotels that don't let you set the room cool enough or have a unit that shuts off in the middle of the night. No problems here, we had a nice, cool icebox of a room! I didn't have a car but I heard other guests complain about the tiny parking garage and lack of parking spots. Apparently there is an overflow parking lot across the street, but that just screams that the property has inadequate parking for its guests. 
The best part of this hotel is the staff! Every single person I dealt with, from maintenance to the front desk, was super friendly and welcoming. Always smiling and always helpful, I truly felt like part of the family whenever I walked in the door. They even had warm cookies at the desk in the afternoon (and free coffee in the lobby at all hours). The sad thing is that I liked just about everything about this hotel but you can't change the location and its subsequent annoying train noise. A hotel is supposed to be a place where you can rest and relax after a long day. Because of the proximity to the train tracks and crossing gate and the noise that prohibited me from sleeping through the night, I left the hotel feeling less-than-rested or rejuvenated. And for that reason, I can't recommend it.