The Guarantee issue IMHO is unresolved.
If I was/were a landlord wouldn't accept a guarantee other than a real property title certified by an Escribano. Many Guarantees Truchas being advertised in the media. Salary receipts under the current economy shrinkage is not worth the paper written on. Bank guarantee's have many flaws and depend on the Small print of each bank..? It's not waterproof.
In any case the new Law may pass in Congress but we know that " Hecha la Ley hecha la Trampa" (Done the law done the snare) there will be a hundred loopholes, also will the new Law be strictly enforced? because going to Court over a rental issue may be a long exercise in futility.?
According to the sanctioned rule, the landlords must accept as guarantee any of the following options: real property title, bank guarantee, surety bond, or joint guarantee or personal guarantee of the tenant (salary receipt or income certificate that can join in case of being more than one tenant).
In this case, the problem may be that it is not clear how the owner is obliged to accept them. You can directly refuse to sign the contract - even for another reason - if the type of guarantee does not convince you. “The extension of guarantees is a huge advance. However, it is discretionary, the owner is not obliged to accept, "said González Rouco.