If I put up "No Tresspassing" signs around my property, will it protect me from being sued if people enter anyway and hurt themselves?
No, it will not protect you. It may prevent someone from alleging they didn't know you were on your property. Generally speaking, property owners must take reasonable steps to prevent reasonably foreseeable harm to others on their property. If you have a specific concern or need actionable legal advice tailored to your situation, make an appointment with an attorney.