If you live on the West Coast, it will take you quite a long time to get to Arugam Bay since you will have to cut across the breadth of Sri Lanka and end up on the East Coast. Irrespective of which mode of transport you take, it’ll take you somewhere around 8-12 hours or more to get to Arugam Bay from Colombo. If you’re travelling specifically to Arugam Bay, I suggest you leave out 2 days for travel (one day to get there, and another day to get back). From the perspective of travel time Arugam Bay may not be the ideal destination for a weekend getaway.
There are a few route options available when travelling to Arugam Bay. If you’re up for a long drive, and starting the journey from Colombo, you can take the rout through Ratnapura, Pelmadulla, UdaWalawa, Thanamalwila, Wellawaya to ArugamBay. From Kandy you can drive to Mahiyangana via the 18 hair-pin bends on to Bibile, Monaragala, Siyambalanduwa, Pottuvil Town and reach Arugam Bay. From the south, you can take the highway to Matara, and drive through Tissamaharama and Buttala via the Kataramaga road to Monaragala and continue to Arugam Bay. Of course you don’t HAVE to drive, when travelling in a group the best option is to hire a van or small bus based on the number of travellers in the group.