Even though we live in hot climate, the thinner viscosity property during cold start of multi grade oil should still count. Cuz the oil will still flow faster compared to single grade during initial start up to it should offer better protection during that first few minutes before the engine reach full/normal operating temp. If it makes no difference, there'll be mostly single grade oil used here, but instead it's the other way around.
I guess if it's for old cheap car engine and don't really care much about the lifetime of it, then just use the single grade. Or if you just not going to use the car for long or planning to sell it, then just use that single grade to save money. Otherwise, still better to use multigrade.