Fence is spot on. It will work fine but way to expensive to broadcast. Besides that, you need to treat the weeds early in the year and then spot spray the Mesquite foliage in summer with the leaves turn darkish green.
Treat the weeds with a good product like Grazon Next around mid march. This will burn the leaves off the mesquites so wait on them until they come back strong, probably in May. If the trees are taller than about 8' do as Fence says and basel spray them with remedy and diesel. You can basel spray anytime if you want to get started but since they have no leaves yet, you won't see results until later when the ones you miss leaf out.
Sendero is a good product but I think the old way of treating using Remedy and Reclaim worked better. I believe Dow exaggerated the results to get folks to use the product that doesn't require a license. Also Reclaim and Remedy were going off patent. I commented something like that to the Dow rep and he said to add a little Remedy to the Sendero mix. This is what I started late last year. My mix is about 70% Sendero 25% Remedy 5% Surfactant.
Where are you located at in central Texas Ikana?