I do not have any special advice for you based on which grassy weed that is. Generally, the options are mechanical removal (machines, hand pulling, hoeing), chemical (weedkillers, pre-emergents), or burning. Each has risks, sometimes substantial, and different effects. At the very least I do not see rhizomes in your pictures which might indicate you have a chance at getting ahead of these things.

What do you want to have there eventually? Nature will fill any bare soil with plants in a very short period of time, even if you kill these. If you don't want this grass, plant something else to crowd it out. Find out what is native to your area and will crowd out the grass roots. If you want bare soil for a few months while you build, cover it with black fabric or plastic to prevent anything from growing.

Thank you. Obviously a lot to think about. The lot is about 7000 sq feet. I intend to have a few trees (coconut/avocado/plantain: about 6 in total) and a vegetable patch to grow okra, eggplant and the like on a very small scale. This will leave a lot of empty space for the weeds to flourish. Hand pulling doesn't work unless I dig all around and deeply at the base of a bunch and pull with all my might. Using a weed whacker just decapitates them temporarily. I do not want to use weed killer as I am afraid it may interfere with the plants I wish to grow. Truly between a weed and a hard place.