There are loads of great trails in the area, but 3 that I consider "classic",
and they follow the 3 great ridges. Ken has mentioned the first, which goes
from Grutschalp to Murren. As he mentioned, you can go down to Gimmelwald from
Murren, and that's great. But one can also hike uphill on a diagonal from the
Murren cablecar station, and eventually end up at the restaurant at
Spielbodalp. There you can get a drink and sit at a picnic table and watch the
cows. You can see that trail and others here:
http://www.gimmelwald.com/pics/gimmelwald/hikemap.jpg
The second goes from Mannlichen to Kleine Scheidegg. The walk itself is
about 2 hours, and we save this for the sunniest day, because of the panoramic
views. (Leave in the morning--most afternoons the peaks cloud up!) Take the
train from Lauterbrunnen to Wengen, then a 5 min walk to the cable car
station, where you take the cable car up to Mannlichen. Once up, you can look
left at a 30 min up and back trail to a lookout point. If you look right
there is the main trail that leads toward the Jungfrau mountain, which takes
1.5 hrs and you end up in Kleine Scheidegg, where you can catch a train down
to Wengen and finally Lauterbrunnen. Great panoramic views all along the
route.
The 3rd classic trail is from First to Bachalpsee. Take the Lauterbrunnen
train down to Zweilutschinen. Get off to switch to the train going up to
Grindelwald. Once in Grindelwald, walk about 20 min further into town to get
to the cablecar station, where you take it all the way up to First. From there
walk south to Bachalpsee. There are trail signs, and it is about 45 min each
way. On a sunny day, you can get great pictures of the mountains reflected in
Bachalpsee, which is a small lake. Just Google image "Bachalpsee" and you'll
see what I mean.
Finally, if you get a foggy or misty day, you can walk further up the Lauterbrunnen valley to Trummelbach Falls, which is about an hour each way (or take the PostBus). Google image it to see why it is worth seeing, and the nice thing is you can actually see it just fine on a dreary and foggy day.
As for costly meals, yes, that can be true. However, we make make good use of the Coop and Migros stores as much as possible. There is a Coop store pretty much opposite the Lauterbrunnen train station. While there, try a bottle of "Rivella" soft drink, which is unique to Switzerland.