The worst thing about Sandbox mode is the fact that everything in the region is automatically unlocked. I don't like that one bit.
But be warned - with the highest speed setting disabled, it takes a large amount of time to get money that you need in order to create more zones or set up new services. I have played the game for 10 hours and I can tell you - you need to be very very patient. If you can do that, you will get a great sense of achievement. If not, you will be frustrated. Also note:
You CANNOT delete a city and restart a new one in its place. You can only abandon it, and whoever claims it after that will start from where you left off. So if you left the city with $0 and negative income, good luck!
Another advice: Plan in advance. Because of the time required for generating cash and the fact that any building, whether private or government, will be destroyed as soon as the road connected to it is bulldozed. So, if you didn't plan and then later need to build a high school or large park (and you will), then be prepared to have a lot of buildings/roads destroyed.
So, in short, be careful when spending money. And be patient. Or else, play in sandbox mode