Edit: I saw the link to this on the main page and assumed it was in TravelBuzz! or somewhere, without realizing it's in SPG. I did make some comments about the Lima Sheraton but what does the OP's question have to with SPG? This should probably be moved.
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If you're going on business and restricted to Lima, it highly depends on the weather - I was in Lima in July and while it was sunny and 75 for the most part, the smog did get a bit thick at times. Not too terribly much to do within the confines of the city, though the Stellaris Casino at the JW Marriott does have a comps program, and in addition to a great $2K run at the blackjack table and unlimited Pisco sours (the amazing Peruvian drink), I got a free 4-course meal at the restaurant
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If you're going for pleasure or have some free time, hop a flight to Cuzco and if you have enough time to spend two nights in Cuzco, use your full day to go to Machu Picchu - you won't regret it
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If you're stuck in the Lima area, go to the chapel of San Francisco and take the tour in the underground catacombs (it's like 50 cents). Also make sure to go to some local cevicherias for the awesome fresh ceviche, and check out the cigar shop in the oceanfront mall directly across from the Marriott for good-priced Cubans.
If it's just a short day trip from Lima you're looking for, take a taxi into the hills about 40 minutes out of town for good photo ops.
As far as hotels go, the Sheraton is considerably cheaper than the JW Marriott but when I went they were full, so they accommodated me at the Marriott, and even called me a week in advance to let me know this. I called the Marriott to confirm my booking, who in turn had a limo waiting at the airport for only US$23. I think the Marriott usually runs >$150 a night, but I had paid $45 a night for the Sheraton and paid no extra for the Marriott.
The currency is the nuevo sol and I think it's about US$3 = Sol10... pretty much, everything is dirt cheap. Like, the most-expensive-thing-on-the-menu-is-five-bucks kind of cheap. US dollars are accepted in many places, and are the only currency accepted in the casinos. Many ATMs dispense both USD and Soles.
Anyways, have a great trip!