I wish we were able to cat proof our garden. Unfortunately, our front (only) door opens onto an open plan lawn area and short of fencing our neighbour in too, there's no way we can make it so the cats can't get out of the garden. Baldrick was supposed to be an indoor cat only as he's nearly blind but as soon as he could get down the stairs he wanted to go out. He scares me stupid every day, he likes to sit in the road (we're on a quiet estate but not everyone has the brains to stop for a cat in the road - the times I've run outside screaming blue murder at a speeding motorist.....) and he goes to visit people to keep them company. Even if they don't want company.
He would be so miserable if I kept him in I have to let him out, and keep a very close eye on him. At this time of year it's not quite so bad, he won't go out except to have a wee/poo then comes straight in again (he won't use a litter tray unless he's bursting) but in the summer he'll spend a lot of time lying in the middle of the road
He also goes off for walks with children, then gets brought back by annoyed/embarrassed parents :D He's an ex farm cat and roaming seems to be in his nature.
Once the building of some new houses has fnished behind us (it's nearly done now), I think he'll go back to roaming round the fields and woods behind us instead - we're surrounded by fields on this estate - and I won't have to worry so much. The rest of our cats don't go near the road, they stay in our graden, next door's (he doesn't mind) or in the fields so I don't need to worry as much about them.
The pub I used to work in had several cats and they were all either indoor cats, or just sat on his back wall and never went anywhere and they were all very happy with that so I know it can be done, and in the right house (with a garden that nobody else has access to) I'd cat proof the garden completely. It's either that or I need to move to the middle of nowhere, buy a house surrounded that is up its own private drive by at least 10 or 15 acres of its own land then the cats can do what they like.