Two speeding tickets in two months doesn’t sound like bad luck to me. It sounds like someone failing to learn his lesson the first time.
I don’t know about where you are, but in the UK trying the broken speedometer defence will probably get you a fine for driving a vehicle in an unfit condition, in addition to the speeding ticket.
Yes, but it is your mistake. I guess I see the increased insurance as part of the price you pay. It even has the benefit of “fitting the crime.” You are a bad risk for the insurance company, so you have to pay more.
If your speedometer is broken your guesstamation of your speed is worthless in court. Deal with it, and fix your speedo.
No speed limit sign on the country road? Look up prima facia speed limits in the California vehicle code. In any event there is no country highway anywhere in this state with a 90 MPH speed limit or even 70 for that matter. Before you hit reply 70 MPH speed limits California are only one certin sections of rural freeway, not country roads.
I think you will have a hard time making a valid arguement that 90 MPH should be the speed limit on a country road at night. But if you can more power to you. 
Well since the OP asked for advice here is mine. Tickets from different parts of California cost different amounts. In Urban areas a ticket will cost you a bunch more than the same ticket from a rural area (My last speeding ticket was for 89MPH on Highway 395 up past Bishop, cost less than $100)
So call both courts and ask about traffic school, and the cost involved. Pay and take traffic school for the cheaper one. For the more expensive ticket you can either go to court and ask for a bail reduction (Judge might feel nice that day) or over the phone plead broke, and ask for a payment plan. A word of warning Do not fuck up on the payment plan. If you skip a payment it won’t go away. These things are like savings bonds, the longer you keep them, the more they are worth. Plus if you skip on a payment, and you get stopped again for speeding you will go to jail, without passing Go and without collecting $200.
Oh and did I mention, fix your damn speedo?
First, check with your insurance company. If you can, don’t give them your name, but just see if you can ask a question. I know for my insurance company, you can get 1 point before your rates increase. If that’s the case, you can do traffic school on one ticket and just pay the other one.
If you want to go to court on either ticket, there is an excellent book called “Fight Your Ticket” published by Nolo Press, that covers all kinds of different strategies to win a traffic court case. Hopefully it’s still in print; I bought mine a long time ago. I’ll warn you, though - both of your tickets would be really hard to beat since you were so far over the speed limit. And I’m sure you know that there’s always a chance that the officer won’t show up, in which case the case is usually dismissed. Also, as far as I know, they don’t use other convictions as evidence against you in traffic court, so I wouldn’t worry about that particularly. The case is going to be tried on its own merits. (Unfortunately, neither of your cases has much merit; but there’s not much to lose except your time.) And, there’s nothing to prevent you from going to court and STILL requesting traffic school if you lose, although I think the smarter strategy would be to just go ahead and do traffic school on one of the tickets anyway.
You can try the “broken speedometer” argument; but I’ll tell you right now that’s not gonna fly.
In California they generally issue “fix it” tickets. There’s no fine so long as you repair the problem and get it inspected and checked off by the authorities. I don’t know if a judge would ever cite a person for an additional infraction like that based on court testimony. I did witness one case where the judge did not. A woman tried to argue that her speedometer was broken, and it turned out she was going over 100 mph (That’s 7 million kph in British units 
). The judge completely flipped out and tore her a new one, but she didn’t add any additional infractions to the sentence, IIRC.
That’s all beside the point, though, because as I said, the “broken speedometer” defense is a really lame one.