The pipe would have to be completely waterproof and buried far enough down so that it wouldn't be exposed to varying temperatures in a wide enough range to allow moisture buildup. Condensation forms, gets inside the wires or connectors, and then freezes and it goes kaboom. Then you have to dig...
I can second the recommendation for Unifi APs. I have a small enterprise network running in my house with two UAP-ACs and it's absolutely fantastic. Manage it all from a java applet in your browser, and it's fully featured. Definitely the way to go without breaking the bank.