  We examine a condition on a simply connected 2-complex X ensuring that groups
acting properly on X are coherent. This extends earlier work on 2-complexes
with negative sectional curvature which covers the case that G acts freely. Our
extension of these results involves a generalization of the notion of sectional
curvature, an extension of the combinatorial Gauss-Bonnet theorem to complexes
of groups, and surprisingly requires the use of L^2-Betti numbers. We also
prove local quasiconvexity of G under the additional assumption that X is
CAT(0) space.
