I'd consider Cotoneaster dammeri. It is evergreen, spreads easily and rapidly and is deer tolerant and drought tolerant once established. It also blooms with tiny white flowers that eventually become bright red berries.

How densely you plant it depends on how rapidly you want it to cover.......a single plant can have a signification spread in time (as much as 12'). Generally, the recommendation for a medium fast coverage without crowding is 18-24" on center but you can space wider or closer if you wish.

Note: don't plant in rows or straight lines but in a diagonal or zig-zag pattern. Much better and a more natural look.

Thanks Gardengal! Appreciate the advice.

Do keep in mind that you will not be able to walk on that groundcover at all. It's not a perennial but a shrub that grows low and spreads. Another shrub possibility for you would be Rhus aromatica 'Gro Low'.

You can certainly walk on a Cotoneaster groundcover. It will tolerate foot traffic easily, which is why it is often used as a groundcover in commercial parking lot applications (parking islands). It just doesn't have the same even surface something like a lawn or a mat-like groundcover would produce so not as comfortable to walk on but still immensely tolerant of foot traffic.

FWIW, there are scores of woody-based or flattened shrub-like groundcovers available - cotoneaster, kinnikinnick, ceanothus, Rubus calycinoides, salal, wintergreen, junipers and various vaccinium to name a few. While not offering a smooth, flat surface like a lawn, they are all walkable and handle foot traffic easily.