But isn't the OP asking advice as a follower?
I think the OP is asking for advice for a couple - and i think you are right that probably neither follower nor leader advice is all that applicable for the OP and her husband.
In some ways a very different question, as they are going to have a built in dance partner - they don't need to impress each other to be allowed to dance

. As Steve Pastor pointed out as long as they are able to somehow move down the line of dance they will be fine. Maybe even if they aren't - i have seen couples who by accident stuble into a milonga, decide that everybody looks friendly enough, and spend the evening watching and slow dancing prom style. And they seemed to have a blast. It probably again comes down more to how comfortable they are with their skills and the situation than how skilled they "objectivly" are.
It is interesting that a lot of people seem to have more fun at milongas at the very beginning than later on (at least that happened to me) - the unconscious incompetence phase of learning is much more fun than either the the conscious incompetence or even the conscious competence phase....
I guess for a couple the question is really twofold:
1) How many lessons to have fun at a milonga dancing with each other?
None!
2) How many lessons to have fun at a milonga dancing with other people?
That is probably very dependent on the milonga - at some milongas you will never get a dance with anybody if you arrive at a couple - and at most it will be more difficult than if you got there seperately. I think this part again has more to do with the social game, and not with anything one could pick up in a class.
(I usually go to milongas by myself, so i have no meaningful experience with that part of the milonga culture - i am actually not sure who here goes dancing as a couple besides dchester?)
Gssh