The Nickelodeon Hotel is closer to Disney and it is visible from Downtown Disney. Universal is about 20 minutes from there. These are the on-site hotels at Universal,
http://www.universalorlando.com/Hotels/Three-World-Class-....
There are also lots of hotels just outside of Universal, check some of the travel sites like Expedia. I am sure they all offer shuttles to and from the parks.
I know Disney allows coolers into the parks with your own food and Universal is not as strict so it shouldn’t be a problem. Universal has two parks Islands of Adventure and Universal Studios, it really depends on what time of year you are coming. The both get crowded in the spring and summer months.