If the pedncle is dry you can pick the watermelon. In reality when the peduncle is dry the plant stop the feed of the fruit. Its not nessesary to have all the plant dry for pick the watermelon. If the interseason is sweet you can have a second watermelon. A fertilizer with oligoelements and of potting soil NPK above the fertiliser and a watering around the plant can help very well the plant to start again after the harvest of the first fruit and help the second fruit to appear and to get fat.
The way to tell if it is ripe is to check the tendril that grows from the node which attaches the melon to the plant. If it is dark brown, then check how large the white spot is on the bottom of the melon. If the white spot is large, then feel of the melon and see if it feels "lumpy/bumpy". A ripe melon develops a distinctive feel. If it passes all three, it is probably ripe.
The sliced melon picture above shows the major flaw with Bradford melons. They tend to have white streaks through the flesh. Fortunately, I had a few melons that did not have the white streaks and have saved seed from them separately. I think I can eliminate the streaks with a few generations of selection.
Average size of Bradford watermelons is between 25 and 45 pounds. I had one 45 pounder this year. Bradford tends to keep making watermelons on the very large vines. In other words, it will mature a melon and then put energy into the next watermelon on the vine.
Bradford watermelons have several flaws which is why they fell out of favor as commercial watermelons. The rind tends to be thick which prevents splitting during shipping. This is a detraction because a larger percentage of the melon is not edible. They tend to have white streaks through the flesh which detracts from visual appeal but does not really affect eating quality. They are larger than the average market watermelon today which means fewer people would purchase one.
On the positive side, flavor is usually outstanding, among the best I've ever eaten. Two of the watermelons I ate this year would have ranked as top 5 melons of all time. I had a Jubilee 25 years ago that was a top 5. Three years ago, I had a Yellow Moon And Stars that was top 5. Last year I had a Ledmon that was top 5. The atmosphere is kinda rarified when you get into the top 5 melons from 50 years of watermelon growing and including about 100 different varieties. One other trait that is a bit unusual is when you cut one with a knife, the watermelon does NOT split. You have to slice it all the way.
I saved seed of just almost all the melons I ate this year. The two best are in separate paper plates drying. Interestingly, one of the best had very large seed which is a trait in demand in China where roasted watermelon seed are commonly sold by street vendors.