I always go to WDW by myself, a couple times a year, and I have never found the meal plans to be worthwhile.
Here's why: In general, even paying ala carte, you will spend less money on your meal than you would with the dining plan UNLESS you go to a signature meal every single day.
Between snacks and meals, you will have leftover credits on your meal plan almost every single day.
Also, when you are a solo traveller, you will find it next to impossible to predict your exact meal times UNLESS you specifically plan your whole day around your meal.
For example: you might plan a late lunch meal for The Hollywood Brown Derby at 2:00 pm....but by 2:00 you will be completely done with DHS and on a bus on your way to another park. As a single visitor, unless you really drag your feet and linger all over the parks, you will find that ALL of the parks are half-day parks if you get started at park opening time. With a family, you'd be lucky to finish half your agenda -- by yourself, you will have done everything there is to do by 2:00 in any of the parks, and be on your way elsewhere having even done a repeat ride on Soarin' (just saying).
I'd do the math and decide how much you are going to spend per day.
I find I get coffee and a danish in the morning (6 bucks); eat a nice sit-down lunch (20 - 25.00) and get something light for dinner off a counter service menu, or something down at DD (about 11.00)...Cheaper than the meal plan for sure. Sometimes I don't want ANYTHING from the parks, and find myself getting some milk and entemann's donuts at the resort shop...
You have the flexibiity to do whatever you want when you are alone. Do you want to spend it all planning around food?