Hide Default "Please enter a value greater than or equal to ..."

You would view the source, get the ID of the containing div and then hide that element with a CSS rule.. something like this example.

[css]
body .gform_wrapper li#field_12_15.gfield .ginput_container div.instruction {
	display: none
}

you would of course replace the "field_12_15" with the actual ID of the field in your form.

You could also apply this to hide ALL of the "instruction" fields in your form by doing this..

[css]
body #gform_wrapper_1 li.gfield .ginput_container div.instruction {
	display: none
}

just replace the "gform_wrapper_1 " with your actual form ID.