Route 7's grass is all tall grass, so anything you encounter there is going to be in twos- though not necessarily alongside another of the same as itself.  The pokemon here come in the levels 26-33, varying by Pokemon.

In addition to Deerling, Tranquill, Zebstrika, Watchog and Foongus, you’re also going to see two or three new potential catches, depending on the season.  In any season, you can find both Zangoose and their foe Seviper on the route.  Zangoose is a Normal-type pokemon with decent Speed and a frankly massive Attack power, which has the ability Immunity, making it impossible to poison.  Nothing too shocking here- Zangoose is a flexible and strong physical offense pokemon with a few basic support options.  Seviper doesn’t match Zangoose’s speed at all, though it has fairly strong Attack and Special Attack stats and comes with the Shed Skin ability, giving it a one-in-three chance at the end of each turn of losing any status effects on it.  Seviper is much more special-effects oriented than Zangoose, though, supporting its array of physical attacks with things like Haze, Crunch, and Glare.  Sadly, it lacks the special attack options to really make use of its twin high attack stats, and its defenses are mediocre at best.

During winter, Route 7 is rife with Cubchoo, one of Unova’s pure-Ice-type pokemon.  Cubchoo has the Snow Cloak ability, making it harder to hit in a hailstorm and it’s a good thing it keeps that ability when it becomes Beartic given the poor typing that pure Ice is.  Beartic has a physical attack comparable to Zangoose’s, though it loses badly on Speed in exchange for some fairly hefty defensive bulk.  This would be all well and good, but Beartic is sadly lacking in naturally learned high-power attack moves, and with Avalanche no longer a TM it has remarkably little access to Ice attacks that really work with its stats.  If you are willing to invest in Move Tutor learning and the Reminder Girl at the National Tournament, you can pump it up a bit with things like Superpower, though, which makes Beartic terrifying to other Ice-type pokemon.  If you can avoid the varied vulnerabilities of an Ice type, Beartic is one of the more powerful ones you can use, so long as you have a way to either improve its speed or crank its endurance to the point it no longer cares that it goes last.

At the start of Route 7 you’ll notice a narrow wooden walkway- as long as you’re careful, you can use this to reach the far side of the tall grass without stepping in any, and without attracting the attention of any trainers.  Keep moving, though, or you’ll start to fall off.  Running is also a good way to accidentally dismount, as it’s harder to make the precise turns you need to not launch yourself into the air.