I went to Sirmione last summer with a friend for a week, and as we were on a tight budget, being students, we chose the Hotel Grifone, and I think we ended up paying about £20 a night each for a twin room, in the middle of July! We didn't get breakfast, but that was fine for the price.
You can't expect a great deal for that kind of money, and the rooms were very basic, no TV, coffee-making, phone or anything like that, and unfortunately our room lacked air-conditioning, although we saw into some of the other rooms and they did have it. Best to specify that you want it if you're going. There aren't many rooms so perhaps book early.
We did have an en-suite shower and toilet, though, the beds were perfectly comfortable, and the room was very clean. We also had an amazing view of the lake - the hotel is actually on the edge of it, and has a little stony beach at the end of the cul-de-sac on which it is situated.
The location is probably the best thing about this hotel, other than the price. It is inside the historical centre of Sirmione, which is beautiful, if entirely overrun by tourists at that time of year. There are shops, restaurants all around the place, and it is right next to the castle, which is one of the main tourist attractions. The problem with Sirmione and a lot of the villages around the lake is that they are so small, so they tend to have large areas outside them, which can extend for miles, which are occupied by residential areas and tourist hotels and apartment blocks, so you could find yourself in a decent apartment with a pool and so on, but several miles away from the actual village. Always check how close these hotels are to the centre.
The staff were friendly and helpful, gave us maps and directions to places we wanted to go, called taxis etc. Another good thing about the hotel is that it has a superb restaurant joining onto it, which is mainly why the place has its reputation, with indoor and outdoor seating areas. The outdoor part is absolutely beautiful, overlooking the lake. The restaurant has beautiful fresh sea food and I would highly recommennd it.
All in all, it was a really nice place to stay, as long as you're prepared for the basic rooms and facilities.