Best time to visit Bratislava is in July and August, but the city is packed with tourists and prices are high. If you want to enjoy Bratislava, then May, June and September are ideal, with moderate temperatures and hotel prices, and a chance to see everything the city has to offers, on your own time.
April and October are fairly cold and rainy, but you can find great lodging deals.
Slovak winter may be cold and chilly, yet you can find amazing hotel deals. Hotel prices are at lowest, with a wide selection of lodgings. The city is also famous for bachelor party activities, therefore you can plan ahead for a crazy trip with friends.