Jambo, sailanacra is spot on. June - September is the dry season, fewer bugs (which can include malaria-transmitting Anopheles mosquitoes,) the animals beocme more concentrated and come to the boreholes, as there are no other regular sources of water (perhaps a few of the low-floing rivers, but Salt Lick waterhole is a serious magnet.)

Nairobi is known for "Nairobbery," scammers and has had some security problems. But it is seasy to stay out of trouble - avoid the bad areas of town and walking ANYWHERE after dusk (much less ALONE after dusk,) take reliable taxis / cars, follow the recommendations made by your hotel / providers. Mind you, there are areas of Cape Town, Mexico City, New York, Los Angeles and myriad other cities I would give similar advice about... but I'd not hesitate to go. The Hilton itself has pretty decent security, can pick you up at the airport and recommend good drivers / providers (like Let's Go Travel or Bruce Travel in Nairobi - reliable and economical for other tours, etc.)

In Nairobi, a tour to Karen (suburb) and Blixen House, the Langata Giraffe Centre (you can see a very posh place to stay thorugh the trees, Giraffe Manor,) and it seems everyone winds up diving at Carnivore... I'd also recommend the National Museum, particularly for the stunning watercolours of different native peoples by artist Joy Adamson, better known for her "Born Free" escapades with husband George (the "rest of the story:" when we were camping in the Aberdares, we had to be careful - those lions released back into the wild did OK, but they were no longer afraid of people and killed a couple...)

Nairobi National Park is a good place for a half-day trip - there is plenty of game, within view of the city! I also highly recommend Richard (Dick) Estes' brilliant book - how to id and behaviors with incredibly useful easy to use b&w line drawings, not pretty photos: The Safari Companion: A Guide to Watching African Mammals Including Hoofed Mammals, Carnivores, and Primates (Paperback, about $20.) This will really give another dimension to your trip - and is perhaps second best to what I did, which was travel with Dick.

I'd frankly avoid the rainy season - the roads get very nasty, the animals disperse, the mosquitoes come out in force... and if one wants more wildlife, arrange a trip down to the Masai Mara - July and August the migration is "in" from the Serengeti to the south, and it can be brilliant!

Finally, please do a "Search" on this forum using key words like Salt Lick, Nairobi or SAF8. Much will be revealed, many have posted. (Oh, I am sure SD1K knows this, but it is not the "Lama Suite," that's in Tibet - try for the Lamu Suite, named after the island off the northeast coast of Kenya that is the birth of the Swahili culture - and an interesting palce to visit, I may add.)

Kwa heri, JDiver