Ants are not leaf eaters. In general, the reason you have ants on plants is that you have aphids. The aphids exude a sweet sticky substance called honeydew that the ants like. It is a little circular because, as tom noted, sometimes the reason you have aphids is that you have ants - the ants actually "farm" the aphids to get the honeydew and will bring the aphids to your plants. So you need to get rid of the aphids and then you have to watch out that the ants don't bring more back.
But it is all basically hygiene. Soapy water solution takes care of the aphids and just water takes care of the ants. If it is a specific plant you are worried about, you can help by covering the ground around it with some kind of powder - flour, baby powder, powdered chalk, etc. The ants don't like to crawl over powder which clogs their spiracles up.