If you are planning to watch the Delta IV Heavy NROL-15 launch on Friday morning then you will probably find that there will not be too many people joining you and you will be able to get your pick of viewpoints.
There are 2 great locations, SR-401 by the Cape Canaveral Air Force Station gates and Jetty Park. Moving further afield just about anywhere on Cocoa Beach will get a good view, but not until the rocket has left the pad.
As the launch is just before dawn Jetty Park is likely to be shut so that really only leaves the option of the SR-401. This is about 8 miles from Launch Pad 37B and has a full unobstructed view of the rocket over the waters of the Banana River.
There are no facilities at all here, but plenty of parking so come prepared. Click here for a detailed Google map.
Back in January 2009 a Delta IV Heavy launched with NROL-29 payload. The following video shows the view that can be seen from the SR-401 viewpoint.