Tres cocos is one of the nicest parts of the island. The issues are that there is no trash pickup (unless you pay), city water or good roads. The roads issue may change soon. The land in the area is expensive but a little less so than the Holiday Lands area to the south.
Holiday Lands area south has no issues but there are very few lots available and the price is above the tres cocos area.
Talk to a Real Estate agent (www.ambergrisrealestate.com
) and visit both areas and then make up your mind (that was a shameless plug).