I live in a semi located on a corner of a road and we are constantly
disturbed by youths sitting on the garden wall, drinking and shouting
until
the early hours.

I solved the problem by putting railings along the top of my section of
the
garden wall, but my neighbour (an old lady of 70-something) can not
afford
anything like this.

Can anyone suggest a cheap (legal!) solution to this problem?

brambles and/or stinging nettles.
Hayley