Instead of checking for return strings I would just check for the return code:
both
svn ls REPOSITORY/PATH
and
svn info REPOSITORY/PATH
return 0 if all went fine, and 1 if things went wrong; you can quickly check it out:
echo $?
so in a bash script just do something like:
error=$?
if [ $error -ne 0 ]; then
YOUR ERROR HANDLING
fi
works like a treat!