My boyfriend and I stayed in Casa Rustica for 3 nights over New Years. As other people have discussed, the noise level was very high, although we did expect this having read the reviews and with it being New Years week. There was a rooster every morning that kept us up, and I know of another couple who switched hotels because of this. It didn't bother us too much, but something to note. The noise level is, as others have said, high.
That said, we thought the hotel was average. We loved the location and loved the rooftop patio. It was quiet, a good place to lie and read a book and had a fantastic volcano view. We originally booked our hotel for 4 nights and when we needed to switch to 3 in order to squeeze in a trip to Semuc Champey, we were given a lot of grief. We appreciate flexibility in hotel staff so found this frustating. Finally they agreed to let us only stay 3 nights (we hadn't paid yet, so it wasn't a matter of giving a refund, it was just changing our reservation). We emailed them this change a month in advance and they said no. In person we asked again, and had to fight them a bit on it before they finally agreed, although ended up charging us 15% of the 4th night that we never stayed. Other hotels are much more flexible so this was frustrating and made us like the hotel less. The hotel was clean; no bugs. All in all, decent hotel, great location, not so great service.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC