First off, you can still go ahead and make ADRs! You don't need to be on the dining plan to make ADRs.
You're trying to save money.... But you can eat in a manner somewhat similar to the DDP, for less money than the cost of the DDP!
So some of the pros -- Instead of being stuck with an exact allotment of TS and CS meals.... You can eat the exact number of TS and CS meals that you actually want to eat.
If you want to have an appetizer as your whole meal (whether for cost savings, or simple preference), you can now do that!
By skipping the DDP, you free yourself to eat at restaurants on and off-site, that don't accept the DDP! The Swan/Dolphin have some great restaurants, and you can even save money at that with restaurants.com certificates.
But overall..... You can save tons of money, while getting a dining experience that is personally tailored to your actual preferences.
This! This! 100 times THIS!
You have a car and a kitchen. Go to Publix and buy cereal, milk, OJ, pop tarts, muffins. Whatever you normally eat for breakfast. DO NOT STEP FOOT IN A RESTAURANT FOR BREAKFAST. EVER! Your total grocery bill for the whole vacation for breakfast will be under $50. And buy generic bottled water while you are there. Buy a couple bottles the size that you would want to carry around, and then buy a 5 gallon jug to keep in your condo. Refill the carry-around bottles every morning. (Or, if you don't mind the tap water, just refill with that.) Total water cost for the whole trip is less than $10.
When you eat a TS dinner, which you can, and still should do, buy one appetizer for every 2 people in the group to split. Same with desserts if you opt for that. And if an appetizer looks really good, have it as your entree. When you dine like this, you will still get plenty of food, but you will save a lot of money.
Assume the DP costs $50 per person. (Using round numbers here).
4 adults over 10 years old will cost $200 per day.
Can you beat $200 per day? Sure.
Assume you spend $100 at Publix for breakfast, water, snacks, soda. For a 6 day trip, this nets out to $17 per day.
Total so far=$17.
Assume 1 CS per day and 1 TS per day. You choose whether it will be lunch or dinner.
CS for 4 people will be 4 burgers/entree salads/wraps/ribs/chicken or equivalent. Average cost is $10 per person for $40. Get 2 orders of fries instead of fries for every person, and get 2 large sodas to split between 4 people. Total cost for those is $7 for fries and $5 for sodas. Total lunch cost is $52. Snacks and water are already paid for at Publix.
Total spent so far is $69.
You have $131 left over for a TS meal.
4 entrees at a non-Signature restaurants, average of $24 per entree, is $96.
You have $35 in savings per day to this point. Share a couple of desserts and you reduce the savings to about $20 per day after tax and have eaten basically the same way that the DDP provides for.
If you stop right there, you save around $20 per day and have had a full Disney experience, although this will not include any character meals. And this assumes that every person ordered their own meal at the CS and every person ordered their own entree for dinner. Split some meals for smaller eaters, or have appetizers instead of full entrees and the savings increase. So much so that you can probably toss in a character meal. And every single meal was a Disney meal. Eat at a family-style restaurant off-site a couple of times and those $24 entrees on average will fall to closer to $17. That's $7 per person, or $28 more in savings. The savings will really pile on and a character meal will easily fall within your budget.
Saving money off the plan is easy and not at all punishing. Just ask yourself. "Does every person in my group need a full CS meal including dessert every day, plus their own entree with dessert every day, plus a Disney snack every day, or will we be just as satisfied having dessert only with dinner, and then, only every other day. Or every day, but split among 2 people?" If you are willing to eat in-house for breakfast and eat less food than the DDP provides at each CS and TS meal, then cost savings are pretty much guaranteed.
Now....having said all this, the PP makes some good points. The rental car fee, gas and parking may devour your savings. You can do everything I suggest above and stay at a Value. You can have groceries delivered to your room. Bring a collapsable cooler with you and fill it with ice twice a day to keep milk and OJ cold. You won't be able to do off-site meals, but that might be OK since you aren't paying for the car.