Belgium has a very good public transportation system. It starts at the airport in Zaventem, a suburb of Brussels. Here you can just go down the escalator -or elevator- and find the train station. There is a train to Brussels every fifteen minutes and from Brussels you can get to anywhere in the country. Brussels has three train stations: Noord (North), Zuid (South aka Midi) and Central. North and South are the main transfer stations and from there you can find trains that go all over Europe.
You can buy a ticket at a vending machine, a teller window, or even on the train if you are in a hurry. When you step on the train, you have to ask the conductor to buy a ticket-if you don't ask they may charge you for fare evasion. Belgium uses the EURO currency as does most of Western Europe. Taking your bike box on the train is quite easy too, but if you do it is better to avoid morning and evening rush hour on the main lines.
Alternatively you can rent a car. Renting at the airport is convenient but more expensive. A good trade-off is to rent from one of the many rental agencies that have offices at nearby hotels instead. Budget rent-a-car is one of these and their offices are at the Novotel in Zaventem. By locating their offices off the airport, they can offer better prices. Getting to the Novotel -or any other airport hotel is as easy as walking to a shuttle. Budget has a roomy shuttle that can easily transport you and all the luggage you cared to bring to the Novotel. Once there you can pick a car that suits your needs.
You do not really need a car and it is quite possible to get everywhere you want to go by using public transportation. Once you have built up your bike, you can use it to get around. But be careful because bike theft is quite common in Belgium, especially in big cities. Cities with universities such as Gent, Antwerpen and Kortrijk, have an even higher incidence of bike theft and thieves have been known to sweep in with vans and load them up with bikes. It is not advisable to leave your expensive bike outside when you go shopping.
Fortunately most cities are laid out in the medieval star pattern with a central market square and radiating main streets. If you need anything, simply walk to the center where all the activity is. During summer cities have a market day, when merchants put up stalls and sell anything from clothing to sausages and fresh veggies to brooms.
Bed and breakfast places often have bikes for rent. Sometimes the use of a commuter bike is included in the price. Commuter bikes are set up for shopping and getting around. They have wide tires, a basket for goodies, and chain and spray protectors so you don't soil your clothes. If you plan an extended stay you can often buy a used commuter bike for as little as EUR20.
Getting to and from races is just as easy. Wherever you stay you will be well within riding distance to several races. Riding to and from the race is a good way to warm up and cool down. If you stay anywhere in Flanders, you will find races within a 25 km-30 km (15 mi-20 mi) radius nearly every day of the week. Having access to car will give you extra options and you may be able to pick better events, but the difference won't be all that significant for the most part.
One good thing about a car is that you can bring tools or spare wheels. That is less of an advantage than you may think. In most races, when you flat you are out. The speeds are so high and in the youth categories (nieuwelingen and junioren) so near the top end of what you can reach with your restricted gearing, that getting back in is all but impossible. The races also show little or no letup and usually speeds are near max from beginning to end.
The best thing about a car is protection from the weather. That is almost essential in the spring when the weather can be quite miserable. In summer it often does not matter much as temperatures stay high most of the time. You may still get wet riding to and from a race although often storms are transient and waiting 20-30 minutes can make all the difference.
Belgium has rain year round, and in the spring many storms come in from the Atlantic. It is often cold and windy when rain storms hit. Having a car will allow you to get to races dry and warm. When you race in springtime in the rain you will often need a car to warm up afterwards too.