We were wanting to create a "natural" privacy fence along the parameter of our yard, something that is thick and tall enough ( 6′ )to make a reasonable barrier. IS their particular shrubs or trees that would be a good selection that is resonably hardy?

Leyland Cypress…fast growing and thick and tall.

I want to have a vegetable garden this summer, but will be travelling a lot and unable to keep it well watered. What are the best vegetables to plant?

lettuce
spinach
watermelon
water

I want to make a rock filled garden but i wanted to plant flowers in it also. what flowers do well in rock gardens?

The plants that tolerate the reflected heat of rock or gravel mulch are generally known as Mediterranean plants. Many herbs are Mediterranean, like Rosemary, Thyme and Lavender. There are shrubs like Vitex and Cistus, and trees like Olive and Fig and that are considered Mediterranean as well. One warning, though: the soil needs to be well-drained, with sharp sand mixed in for the Mediterraneans to survive, especially if you live where rains can be plentiful, even if not that way every single year. In poorly-drained clay soils they will slowly, or quickly, decline and finally die.

We are moving into a new house and the backyard doesn’t have any trees in it. So, we are looking to plant some. What are some trees that we could plant that tend to grow quicker than say, a weeping willow or an oak. We don’t want to wait 30 years for a full grown tree. I know all trees take some time, but are there any that tend to grow quicker? Thanks in advance.

Al, PLEASE do yourself a favor and stay away from anything that’s advertised as growing five or more feet a year, such as those hybrid poplars. They are extremely short-lived, and in fifteen years or so you’ll be paying someone to cut it down because it’s dead. (Same goes for Lombardy poplars.)
One of my very favorites is the relatively fast-growing pin oak (or its relative, the scarlet oak.) They have gorgeous fall color. Oaks have a reputation for growing slowly, but that largely applies to the white oaks, which can live hundreds of years.
Silver maple is fast-growing, but not particularly attractive. (Contrary to one answer, Norway is a very slow grower.) I’d try a hybrid, like Autumn Blaze—it’s a cross between silver and sugar maples. It grows quickly the the former, but has the beautiful fall color of the latter.
Birch grows quickly if it’s given enough hydration, but stay away from the pest-prone white paper birch. The river birch is pest-resistant and has pale bark that peels away to reveal a lovely cinnamon-colored trunk.
If you’re interested in an evergreen, my first choice is the Norway spruce—they grow MUCH more quickly than the Colorado blue, and they are just as (if not more) beautiful.
Other trees I enjoy on my property are sunburst locust (which provides filtered shade), Ponderosa pine (very disease-resistant) and sycamore (unusual bark.) In the last twenty-seven years, I’ve planted hundreds of trees and run the whole trial-and-error gamut; these trees would be my first choices for recommendation. Good luck!

which landscaping company is considered number 1 in the Philippines?

Go to Makati city and ask contractor builder of beautiful landscapes