reynosa crossing

ok, i am sure this has been posted many times, but I am a little thick headed. I am driving back from Texas to Ajijic and am planning on crossing at Reynosa. Is everything at immigration needed to get my vehicle permit open 24 hrs? I was planning on crossing around 6 am to get a early start but I am afraid something I need won't be open. Also is SLP or Zacataces the best/safe route. any suggestions as to where to stay overnight on either route? I have never brought car in or driven down before. Any help is appreciated