After reading the reviews in Trip Advisor I went to the San Martin Hotel with no expectations. I was so wrong.
The hotel is 200-meter away from the Brazilian national park, no shops or restaurants nearby and about 15 minutes from the city of Foz by bus ( which offers good service and the bus stop is just across the street from the hotel)
Following the advise of other guests, we did not stay at the standard room and booked the Junior Suite. ( there are for categories of rooms: standard, superior, superior class and junior suite. both superior class and junior suite are very nice and the superior room is ok as well) The room was spotless, new and modern. Service was quick and efficient, at the reception, pool and restaurant. Breakfast and dinner were buffet, food was fresh and specially for dinner it changed every evening: salads, beef, rice, pasta, and chicken fish or pork, potatoes. Desserts were ok. Love the batido de maracuya! Once a week they offer churrasco for dinner ( barbecue) which was very good.
the pool area is very nice: big pool, big area to sunbathe ( you are given pool towers), lots of shade and a 2.3 km path to exercise. tennis court, football field and playground for kids. In the evenings you can play cards, pool, ping pong or watch a movie.
Next to the hotel you'll find the Birds park which is worth a visit.
My husband and I travelled to Iguazzu thrru an Argentina travel agency, called Ati ,www.ativiajes.com.ar, which owns the hotel and I think you get preferential treatment. They also work with the travel agency desk at the hotel that offers tours in the area. I think that's the weakest point: the guide simply takes you to the falls, etc but does not offer much interisting information.

We had a great relaxing time. totally recomend the place.

This hotel seemed to us to be an old resort that probably used to be a destination in itself, but is now, for most people, just a two-day stopover while visiting the falls. There is a feeling of "faded elegance." The best part is the grounds, which are spacious and well-kept, and include a lovely pool area and beautiful nature walk that takes you down to the Iguassu River. The rooms that once might have been upscale are now clean but basic; they probably haven't been significantly upgraded in ages (if ever). There is new carpet in all the hallways, which was nice, but always people smoking in the lobby.

I think if you don't expect too much from this hotel you won't be disappointed, and will be pleased with the location - it is really nice to be able to walk to the Brazilian falls and to be conveniently close to the airport. We ate two breakfasts and one dinner there, and the buffets were fine for a family with two teenagers.

We picked this hotel due to its location which did not disappoint, however the hotel has beautiful grounds but the interior is all dark giving it a dinghy feeling. We had read previous reviews and seen the photos so we knew what to expect. The bathroom was OK but the bath itself had marks in the bottom of it. Our view out of the room was another building which was only approximately 4 foot away, together with a dripping roof all night. The bedding also looked very dated giving the whole room a dull feel. As we were only here for 2 nights it didn't matter too much however if I was staying longer I would definitely pick another hotel. The staff were OK and there was a tour advisor on hand in reception who was very helpful in craming in our requirements. She arranged for a guide who was very nice and arranged for our passports to be stamped in Argentina (not something always done because of the visitors to the waterfalls in either country). One good thing about the hotel was that it was only 10 minutes from the airport.

We stayed at this hotel for three nights.
The one major hiccup was the standard room. The hotel itself has a lovely swimming pool, grounds etc and pretty good facilities but the standard room was truly appalling.
We tried several of the rooms and they all stank of cigarettes smoke. The room was also not only small but the condition of the shower/hand basin was poor and in desperate need of replacement. There were also no plug sockets/no hairdryer or shaver socket in the room. Having travelled around the world this is the worst "4* star room we have ever stayed in - more like one star.
My wife in particularly was upset over the standard of the room and as a result we were forced to upgrade to a better room (at a price of almost £20 a night!!). Though small it had been modernised and was up to standard.