If I'm supplying a string to be used in a LIKE clause, does LLBLGen escape the string such that single quotes, for example, can't break out of the query?

I've found that I can use % in a LIKE clause and it works as an 'anything before' operator.

If you are asking about SQL Injection:

All SQL generated by LLBLGen Pro is parameterized. This means that no values are embedded into the SQL query being generated. Due to the parameters, a value can never influence the query being executed, as the value will never be part of the query itself, but just a value of a parameter. The generated code is therefore not vulnerable for SQL injection attacks.

Values passed as parameters (i.e. SqlParameter object) do not need to be escaped.