Dear Journey North,
Spring and fall migration are quite different to observe in Texas. I'll describe them for comparison:

Spring Migration
It’s not dramatic, actually, what you see in Texas in the spring. You never see too many monarchs at once. You may see one or two an hour, and that would be a good spring migration. Sometimes along the coast you may see ten or twenty at once, but that would be during a very strong migration. The reason you see so few in the spring is because there are far fewer monarchs alive in the spring than in the fall. There has been mortality at the overwintering sites in Mexico and mortality along the migration. Your chances of seeing high numbers of monarchs at once are not good. They’re just too dispersed.

Fall Migration
In contrast, during the fall migration, you can see many, many, many monarchs at once. It's not uncommon to count hundreds in an hour in Texas, if you're in the right place at the right time. Sometimes when the butterflies are being blown by the wind you can see hundreds in the sky at a time. You also might see hundreds at once at two times during the day: Mornings when they’re just leaving roosts, and also in the evenings when they 'fall out' of the sky and come down to roost.