Well, insofar as the type of touching goes, I know plenty of white kids (and black, and Filipino, and Spanish, and Mexican, and German, and, and, and) who love all over my baby. Their behavior sounds completely normal and is, in my opinion, for *me*, totally acceptable. So, that's me.
But for you, it's unacceptable. So I agree you need to speak to the parents. I personally would say something like: "I'm glad to have nice neighbors like you. Your children are very sweet. But to us, our yard is part of our home. So please, ask your children to respect the gate like they respect the front door. I don't want to keep nagging them. Thanks!"
I wouldn't leave the note. Try your Spanish. Go for it.
It seems to me like you want the parents to do something about something they have no problem with. You don't want to confront them. There are lots of inarticulate people in the world that are shy about bringing up issues, but they do it when they have to. So you're inarticulate in Spanish. That's okay. Maybe it will disarm them, make them more gentle with you. LOL
Quote:
| Ex: "I want M (my 8mo) to be my baby sister for my mom and dad to have and take her home with me..." She then went into detail about how my DD would become her sister. Strange. |
This is so normal as to be common. I must hear it weekly about my baby. They just want a baby sibling. Simple as that. They're not going to steal the baby.

Maybe their parents are done having kids. Probably they said it at home and the neighbors laughed and said, "Oh, I bet her mama would miss her!" or "Are you kidding? You kids are enough trouble for us.

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Quote:
| "Move aside, I need to get to my car and you're in my way," "No, don't come in our gate, we're having family time out here right now," "No, you can't come to the store with us, go home. I know your mom said yes but I'm the one who would have to watch you and I said no." |
I would say all of these things, but with "please" attached, while in a very firm voice with a firm but gentle look, after having explained to them with their parents that the yard is your family relaxing space.