In wireless mesh networks, designing algorithms that efficiently balance the traffic loads among a given set of network gateways is a challenging problem. Links interfere, transfer capacity is limited, and traffic demands vary overtime. The position of the gateways also affects the overall network performance as a result of its direct impact on the way routers are associated to gateways. In this paper, we investigate the performance of several routers-to-gateways association heuristics in relation with different gateway placement algorithms. We show that if bounds on the number of hops between routers and gateways exist, load-based heuristics perform the best. In general cases however, interference-based approaches provide better load balancing.