If I signed an assignment of a lien form through the homeowner's lender - do I still have lien rights?
The legal analysis would start with a review of the assignment document, and the rest of your contract and the lending documents.
Typically, an assignment of lien provision transfers lien rights to the lender to ensure that the lender has the first lien on the real property.
You really should retain a construction attorney to review and evaluate your legal position based on the contract and pertinent documents. The right to be entitled to file a mechanic's lien is set out in Texas Property Code Chapter 53, and you really need to make sure that if you file a lien, you have properly and appropriately done so.
Filing an invalid lien could subject you to liability under the Texas Fraudulent Lien Act, and you could be liable for statutory damages of $10,000, or actual damages, whichever is greater, plus attorney's fees. Facing such a claim would add insult to injury.
Good luck.