A lot of places have zoning restrictions on how high fences are allowed to be. Around here I think it is 6 or 8 feet. If you are in a HOA then the materials might be an issue too.

For concrete work you'll want this thing: http://www.amazon.com/Scepter-04239-7-Gallon-Odjob-Mixer/dp/B000BPK766 You add water, add the dried concrete (in that order), seal it up and roll it around the yard. It make mixing it super easy.

Can you do Leyland Cyprus trees?