Ainsley,
The best time to take the driving test depends really on the individual who is taking the test. Some people find it easier to do it off-peak hours because there's less traffic and it makes them more confortable and more confident. Others find rush hour to be good because you tend to get more stuck in traffic, therefore you're not driving too much.
If you feel that you will be fine during rush hour, then go for it. As long as you're not nervous, you should be fine.
