One model or various separate models

If they are all connected then it sounds like one model to me. I am not certain what you mean by a "block" however. A set of zones or an actual city block?

Ana Paula—If the project consists of several buildings connected only by walkways and parking, you should verify whether the project complies with the Minimum Program Requirement to Use Reasonable LEED Boundaries. MRP2 requires (with some exceptions), “Buildings that have no physical connection or are physically connected only by circulation, parking, or mechanical/storage rooms are considered separate buildings and individual projects for LEED purposes” (http://www.leeduser.com/credit/NC-v4/MPR2). If the project cannot qualify for an exception to this rule, you might be able to follow the “LEED Campus Guidance for Projects on a Shared Site” to certify all the buildings as a single project using the “Group Approach.” To earn this Prerequisite, this approach requires a separate model for each building to show that each complies individually, but the Optimize Energy Performance Credit (EAc2) uses the combined results from the individual models. Similarly, the Group Approach applies special requirements for many of the other Credits and Prerequisites. For more on the Campus Guidance, see the LEEDuser forum http://www.leeduser.com/topic/new-leed-guidance-campuses-and-multiple-buildings. On the other hand, if your connected “blocks” qualify under MRP2 as a single building, a single model should do.

Now it does not sound like one building so follow Jon's advice.

Ana Paula—LEED Interpretation LI#10203 does allow an exception for “K-12 schools, hospitals, hotels, resorts, and resort properties” if, among other conditions, each building is less than 25,000 square feet: http://www.usgbc.org/content/li-10203.