Ok, lets face it. We've all heard stories of child prodigies and the wonders of learning music as a child but how many of us actually have that opportunity. If you're one who thinks that by the first sign of wrinkle, you're apt to plan for retirement, think again. I'll be the first to holler that there's no age limit to learning music. Even with no prior training, yes! You are your only limitation.
Adult learners come with their own baggage different from that of children. It could range from scary instructors who knock their fingers with rulers if they don't perform acceptably, though I do hope these kinds have extinct, or having to look up to the teacher as an authority figure which is hard. Most adults would be happy just to be their own audience.
So the best way is to find an instructor who is able to provide lessons based on the needs of the student, either one that cover both theory and practical, or just practical alone, learning by hearing so there's no loosing sleep over trying to memorize notes.
Don't over complicate things in your mind. If you can picture yourself playing, you could well be on the path of realizing it, adult, child or the in between!