The VIP card is valid and probably worth it if you are staying 2 or more nights in a 3 month period, even if not on Monday or Tuesday. The cheapest room at Cascadas is $150 a night on weekends. For two nights, the VIP card would save you 20% or $60. Then you get 2-4 free drinks in the club and you're past breaking even on the $70 cost. If you're on a tight budget, stay at the Rizo where the rooms are slightly cheaper and the VIP card is only $50.
If you go with a more expensive room, like a room with a jacuzzi, the savings will definitely far outweigh the cost. Especially on a Mon/Tue but other nights too.
Also @Owlyoung_ggofv, I don't think anyway has answered your question on what Azul and Senda Norte cost. They both service decent food (think like a slightly better mexican applebees) and are fairly cheap. Like plan on $25 including tip for a meal and drink for just you, maybe $50 if you take a chica there (which is a high value play and cheap way to spend time with a chica.) The service and ambiance is better at Azul, where you can sit on the balcony and people watch paraditas, mongers, and locals scurrying around below in the alley behind Hong Kong. I recommend the spicy shrimp tacos con queso!
Senda having slow service is actually a good option if you are with a chica and want to maximize your time.
Also, there is a difference between "Restaurante Azul" and "Azul Sports Bar." They serve the same menu. The former has the awesome balcony. The later is all indoors but does have TVs for sports watching, and also sometimes there's chicas milling about the bar too. The sports bar is on the 2nd floor in the back of Cascadas hotel. To get to Restaurante Azul, you have to go out the alley side door from Cascadas, leave the hotel briefly, take a left, and at the next door go upstairs. I mention this because on my maiden voyage, I completely missed Azul, thinking I was in it at the sports bar.
Make sure you give them your VIP card when you get the bill, for the 20% discount. I forget half the time.
I've found that the street tacos at the vendor at the corner of Calle Coahuila and Av. Niños Heróes to be absolutely fucking spectacular, however my CF insists the tacos are made from dogs. If that's true those are some delicious and sanitary puppers because I've always enjoyed and never gotten sick eating there. YMMV.
Outside the Zona Norte if you're willing to take a cab, there are some great restaurants to explore in Tijuana. But you'll definitely be fine with your plan to eat at the hotel restaurants and street vendors for a few nights. You can also get room service 24/7 from Senda or Azul sent to either Rizo or Cascadas!