No. Secure Messengers are designed to be hard to use unsafely. Nobody accidentally sends plaintext to a counterpart with Signal, because there's no feature in Signal that does that.
If you can't trust the recipient, there's nothing you can do. The point isn't to protect yourself from an untrustworthy recipient, it's to protect yourself from inadvertent disclosure.
You can still send text messages (including to Signal contacts by long-pressing the send button). Obviously it is harder than just sending an encrypted message.