Here you go. On towels the accepted distance from the border is 1 1/2 to 2" or 4 inches from the bottom if there is no border.

Washcloths
1" - 1 1/2" above hem, or 1" above border. Can also place design in corner, angled, 1" - 1 1/2" above corner.

Hand Towels
2" above hem, or 1 1/2" above border.

Bath Towels
4" above hem, or 1 1/2" - 2" above border.

Bath Sheets
5" above hem, or 2 1/2" - 3" above border.

This is taken from Embroidery Library's help section

According to Bella Lino "3 inches from the bottom edge or 1 inch above the dobby" (border) for a hand towel.

Here is a link that I hope come in handy not only for this project but many more.