As to digging holes...what is going where?
Landlords hate to pavement and asphalt dug into. Shouldn't be a problem in dirt/grass areas as long as you don't hit underground phone lines and the like.
Due to wind loads, any sign post has to be driven in the ground at least 2 feet, usually more depending on face size. The pre-pointed drive stakes may be good for anchoring a mailbox but not all that good for signs if you do not wish to face liability should they dislodge and hit a car or person.
Why PVC?
For a 10 mil sign 2 nicely painted angle irons is slim and modern looking and super-strong and goes into the ground like butter with a post pounder.
Dressing up 4" x 4" 's with PVC sleeves and a finial cap (use screws on the cap - don't glue) has strength and isn't going anywhere or get a kit such as:
http://www.1800thesign.com/ip4x8.htm or steal this idea:
http://www.promotesigns.com/html/large_corrugated_plastic_construction_signs.php
Both of those should only be used for temp. signs
It is easy to make a complete frame out of PVC just put it together dry first so you are sure everything fits and is square then knock it apart and reassemble it using PVC cement. You can scuff it with Scotchbrite pads and paint it with Krylon plastic paint. Wal Mart usually has a good selection of colors.
