Balatonlelle is a city along the Balaton lake in Hungary.
If you're in the city centre, a good option is to walk towards the highway M7 by yourself. There is a roundabout in the centre of the city, just on the other side of the rails from the main train station "Balatonlelle". Once you are at the roundabout, you have to walk along the street that is in the direction opposite of and thus away from the main train station (and the beach). Just follow the road for roughly 20 to 30min. The street you are on will cross the highway M7 at some point via a bridge. Even though the bridge has a small fence on either side, it is easy to just climb over the fence and walk down to the highway. You can easily walk next to the highway, since there is a wide gras and also stone path next to it. Walk towards the left, away from the bridge. After just 5mins, there are petrol stations on either side of the highway. There's advertisments indicating the petrol stations from afar. It is easy to catch a lift from there. So if you want to go south to Zagreb, walk up on the left side of the highway. If you want to go north to Budapest, walk towards the petrol station on the right side. It's pretty easy, once you are there.
Since the last hostel, called "Unity hostel", closed down in 2011 and sleeping at the beach is illegal and fined by the police, the best option is to stay at the camping site in the centre of the city. If you are in front of the main train station "Balatonlelle", i.e. it is in your back and you are facing the beach, walk left, i.e. south, along the street called Szent Istvan Ut. After about 5mins, there is a camping site to your right. I was supposed to pay 2000 HUF to sleep there in a tent (i.e. in my sleeping bag, since I didn't have a tent), but in the end the camp site owner let me stay in a caravan for 3000 one night. I thought it was a pretty good deal and it was really close to the lake.