This is video explaining how Hotel Reservation can ruin your vacation, or trip abroad, because you have a Hotel Reservation for a noisy Hotel.
A Hotel should be a safe haven, the place where you can relax, and hide from culture shock, your home away from home. Generally, the best Hotel is going to give you American and European style living, while surrounded by a foreign culture fool of noise, traffic, hawkers, vendors, traffic, chickens, and dogs barking. Noise is a huge problem in Hotels, you do not need to accept noise.
However, do you want to keep your windows closed?
It is better to get a 2 day reservation, and extend you stay, then to get a Hotel Reservation for 14 days in a noisy Hotel. Beware of small bed and breakfast, or boutique hotels...
If you want a Hotel Reservation, then you need a room 10-20 stories up, or more, the higher the better, far above the noise of the country.
I am very familiar with Posada Don Carlos. It's pretty quiet, but since it's in a very indigenous part of town, you will have more than your share of chickens crowing at 4:30 AM, or the church bells warning you mass is in 15 minutes, or 15 minutes later, when the local Quasimodo goes all schizo to let everyone know they're late to mass.
That said, I've never actually stayed there, as I live in Panajachel, so as to the particular amenities, I am probably not the best person to ask. There is an evangelical church being built somewhere down by PDC, but, in the tradition of all great Guatemalan constuction jobs, it should be a while, as in a long, long while, before it's completed.